Patent Publication Number: US-10315642-B2

Title: Method for takeoff of a vehicle with a hybrid driveline

Description:
CROSS-REFERENCE TO RELATED REFERENCE(S) 
     This application is a national stage application (filed under 35 § U.S.C. 371) of PCT/SE15/050308, filed Mar. 17, 2015 of the same title, which, in turn claims priority to Swedish Application No. 1450317-1, filed Mar. 20, 2014 of the same title; the contents of each of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a method, vehicle, and computer program product for moving off a vehicle with a hybrid powertrain. 
     BACKGROUND OF THE INVENTION 
     Hybrid vehicles may be driven by a primary engine, which may be a combustion engine, and a secondary engine, which may be an electrical machine. The electrical machine is equipped with at least one energy storage device, such as an electro-chemical energy storage device, for storage of electric power and control equipment to control the flow of electric power between the energy storage device and the electrical machine. The electrical machine may thus alternately operate as a motor and as a generator, depending on the vehicle&#39;s operating mode. When the vehicle is braked, the electrical machine generates electric power, which is stored in the energy storage device. This is usually referred to as regenerative braking, which entails that the vehicle is decelerated with the help of the electrical machine and the combustion engine. The stored electric power is used later for operation of the vehicle. 
     A gearbox in a hybrid vehicle may comprise a planetary gear. The planetary gearbox usually comprises three components, which are rotatably arranged in relation to each other, namely a sun wheel, a planetary wheel carrier and an internal ring gear. With knowledge about the number of cogs in the sun wheel and the internal ring gear, the mutual speeds of the three components may be determined during operation. One of the components of the planetary gear may be connected with an output shaft in a combustion engine. This component of the planetary gear thus rotates with a rotational speed corresponding to the rotational speed of the output shaft in the combustion engine. A second component in the planetary gear may be connected with an input shaft to a transmission device. This component of the planetary gear thus rotates with the same rotational speed as the input shaft to the transmission device. A third component in the planetary gear is used to achieve hybrid operation, connected with a rotor in an electrical machine. This component in the planetary gear thus rotates with the same rotational speed as the rotor of the electrical machine, if they are directly connected with each other. Alternatively, the electrical machine may be connected with the third component of the planetary gear via a transmission that has a gearing. In this case, the electrical machine and the third component in the planetary gear may rotate with different rotational speeds. The engine speed and/or the torque of the electrical machine may be controlled steplessly. During operating times when the input shaft to the transmission device must be provided with a rotational engine speed and/or torque, a control device having knowledge about the engine speed of the combustion engine calculates the rotational speed with which the third component must be operated, in order for the input shaft to the transmission device to obtain the desired rotational speed. A control device activates the electrical machine, so that it provides the third component with the calculated engine speed and thus the input shaft to the transmission device with the desired rotational speed. 
     By connecting the combustion engine&#39;s output shaft, the electrical machine&#39;s rotor and the transmission device&#39;s input shaft with a planetary gear, the conventional clutch mechanism may be avoided. At acceleration of the vehicle, an increased torque must be delivered from the combustion engine and the electrical machine to the transmission device, and further to the vehicle&#39;s driving wheels. Since both the combustion engine and the electrical machine are connected with the planetary gear, the largest possible torque delivered by the combustion engine and the electrical machine will be limited by one of these drive units; i.e. the one whose maximum torque is lower than the second drive unit&#39;s maximum torque, having regard to the gearing between them. In case the electrical machine&#39;s highest torque is lower than the combustion engine&#39;s highest torque, having regard to the gearing between them, the electrical machine will not be able to generate a sufficiently large reaction torque to the planetary gear, entailing that the combustion engine may not transfer its highest torque to the transmission device and further to the vehicle&#39;s driving wheels. Thus, the highest torque that may be transferred to the transmission device is limited by the electrical machine&#39;s strength. This is also apparent from the so-called planet equation. 
     Using a conventional clutch, which disconnects the gearbox&#39;s input shaft from the combustion engine during shifting processes in the gearbox, entails disadvantages, such as heating of the clutch&#39;s discs, resulting in wear of the clutch discs and an increased fuel consumption. A conventional clutch mechanism is also relatively heavy and costly. It also occupies a relatively large space in the vehicle. 
     In a vehicle, the space available for the drive arrangement is often limited. If the drive arrangement comprises several components, such as a combustion engine, an electrical machine, a gearbox and a planetary gear, the construction must be compact. If there are additional components, such as a regenerative braking device, the requirements that the component parts must have a compact construction are even more stringent. At the same time, the component parts in the drive arrangement must be designed with dimensions that are able to absorb the required forces and torque. 
     For some types of vehicles, especially heavy goods vehicles and buses, a large number of gear steps is required. Thus, the number of component parts in the gearbox increases, which must also be dimensioned to be able to absorb large forces and torque arising in such heavy goods vehicles. This results in an increase of the size and weight of the gearbox. 
     There are also requirements for high reliability and high dependability of the components comprised in the drive device. In case the gearbox comprises multi-plate clutches, a wear arises, which impacts the reliability and life of the gearbox. 
     At regenerative braking, kinetic energy is converted into electric power, which is stored in an energy storage device, such as accumulators. One factor impacting on the life of the energy storage device is the number of cycles in which the energy storage device provides and extracts power to and from the electric machines. The more cycles, the shorter the life of the energy storage device. 
     When moving off a vehicle comprising a hybrid powertrain, the combustion engine and/or electric motor may be used to accelerate the vehicle from a standstill state to a desired speed. 
     The document EP-B1-1126987 shows a gearbox with double planetary gears. Each sun wheel of the planetary gear is connected to an electrical machine, and the internal wheels of the planetary gears are connected with each other. The planetary wheel carrier in each planetary gear is connected to a number of gear pairs, so that an infinite number of gear steps is obtained. Another document, EP-B1-1280677, also shows how the planetary gears may be bridged with a gear step arranged on the combustion engine&#39;s output shaft. 
     The document US-A1-20050227803 shows a vehicle transmission with two electrical machines, connected to the respective sun wheels in two planetary gears. The planetary gears have a common planetary wheel carrier, which is connected to the transmission&#39;s input shaft. 
     The document WO2008/046185-A1 shows a hybrid transmission with two planetary gears, wherein one electrical machine is connected to one of the planetary gears and a double clutch interacts with the second planetary gear. Both planetary gears also interact with each other via a cogwheel transmission. 
     SUMMARY OF THE INVENTION 
     Despite prior art solutions in the field, there is a need to further develop a hybrid powertrain to achieve moving off of a vehicle. 
     The objective of the present invention is thus to achieve moving off of a vehicle, which is equipped with a hybrid powertrain. 
     Another objective of the invention is to provide a novel and advantageous computer program to achieve moving off of the vehicle, which is equipped with the hybrid powertrain. 
     With the method according to the invention, an efficient moving off of the vehicle, which is equipped with the hybrid powertrain, is achieved. The vehicle is moved off from a standstill state of the vehicle, or from a state where the vehicle is travelling at a low speed. When the vehicle&#39;s driver moves a speed control to a desired state, the electrical machines are controlled in such a way that a torque is generated in the output shaft. The vehicle will then accelerate to the desired speed with the assistance of the combustion engine and power from an energy storage system, such as an electrical accumulator, which is supplied to the electrical machines. While moving off the vehicle, the planetary gears&#39; rotatable components are disconnected from each other and a suitable gear is engaged in the gearbox. 
     According to one embodiment of the method, the first electrical machine is activated to exert a first torque, and the second electrical machine is activated to exert a second torque, wherein the size of the first and the second torque influence the power output from the first and the second electrical machine to the output shaft. Thus, it is possible to select a first and second torque from the electrical machines to obtain a certain power output. 
     The electrical machines, which are connected to the planetary gears, may generate power and/or supply torque depending on the desired operating mode. The electrical machines may also, at certain operating times, supply each other with power. 
     The gearbox may be equipped with a number of gear pairs, comprising cogwheels that may be mechanically locked with and released from a countershaft. Preferably, the first main shaft and the second main shaft are connected to a transmission device, comprising a number of connectible and disconnectable gear pairs. The gear pairs comprise cogwheels, which are mechanically lockable with and disconnectable from the countershaft. Thus, a number of fixed gear steps is obtained, which may be shifted without torque interruption. The cogwheels that may be locked on the countershaft also result in a compact construction with a high reliability and high dependability. A gear pair may thus be disconnected, whereat the corresponding cogwheel is disconnected from the countershaft, and a gear pair may be connected, whereat the corresponding cogwheel is connected to the countershaft. Alternatively, pinion gears in the gear pairs may be arranged to be lockable with and disconnectable from the first or second main shaft. 
     Each of the gear pairs has a gearing, which is adapted to the vehicle&#39;s desired driving characteristics. The gear pair with the highest gearing, in relation to the other gear pairs, is suitably connected when the lowest gear is engaged. 
     Suitably, the first planetary wheel carrier in the first planetary gear is directly connected with the combustion engine via the input shaft. Alternatively, the first planetary wheel carrier is connected with the combustion engine via a coupling device. The second planetary wheel carrier in the second planetary gear is preferably directly connected with the second main shaft, and therefore with the transmission device. Thus, a hybrid powertrain is achieved, which may transfer a large torque to the output shaft and the therewith connected driving wheels in all operating modes, without being dependent on electric power from the energy storage device. 
     The first planetary wheel carrier in the first planetary gear is preferably connected with the second sun wheel of the second planetary gear. The first sun wheel in the first planetary gear is preferably connected with the first main shaft, and the second planetary wheel carrier in the second planetary gear is preferably connected with the second main shaft. Thus, a transmission is obtained, which shifts gears without torque interruption. Alternatively, the first planetary wheel carrier in the first planetary gear is connected with the second internal ring gear of the second planetary gear. Alternatively, the first main shaft is connected with a first internal ring gear arranged in the first planetary gear. 
     By connecting a first planetary wheel carrier in the first planetary gear, connected with a second sun wheel in the second planetary gear, a first sun wheel in the first planetary gear, connected with the first main shaft, and a second planetary wheel carrier in the second planetary gear connected with the second main shaft, a transmission that shifts gears without torque interruption may be obtained. 
     With the gearbox according to the invention conventional slip clutches between the combustion engine and the gearbox may be avoided. 
     A locking mechanism is arranged to fixedly connect the combustion engine&#39;s output shaft with the gearbox housing. Thus, the first planetary wheel carrier will also be locked to the gearbox housing. By locking the combustion engine&#39;s output shaft with the locking mechanism and the first planetary wheel carrier with the gearbox&#39;s housing, the gearbox, and thus the vehicle, becomes adapted for electric operation by the electrical machines. The electrical machines thus emit a torque to the output shaft of the gearbox. 
     A first and second coupling device is arranged between the planetary wheel carrier and the sun wheel of the respective planetary gears. The task of the coupling devices is to lock the respective planetary wheel carriers with the sun wheel. When the planetary wheel carrier and the sun wheel are connected with each other, the power from the combustion engine will pass through the planetary wheel carrier, the coupling device, the sun wheel and further along to the gearbox, which entails that the planetary wheels do not absorb any torque. This entails that the dimension of the planetary wheels may be adapted only to the electrical machine&#39;s torque instead of the combustion engine&#39;s torque, which in turn means the planetary wheels may be designed with smaller dimensions. Thus, a drive arrangement according to the invention is obtained, which has a compact construction, a low weight and a low manufacturing cost. 
     The coupling devices and the locking mechanisms preferably comprise an annular sleeve, which is shifted axially between a connected and a disconnected state. The sleeve encloses, substantially concentrically, the gearbox&#39;s rotating components and is moved between the connected and disconnected state with a power element. Thus, a compact construction is obtained, with a low weight and a low manufacturing cost. 
     In order to connect, with the first and the second coupling device, respectively, the sun wheel and the planetary wheel carrier of the respective planetary gear, the combustion engine and/or the first electrical machine and/or the second electrical machine is controlled in such a way that a synchronous rotational speed is achieved between the sun wheel and the planetary wheel carrier. When a synchronous rotational speed has been achieved, the coupling device is shifted, so that the sun wheel and the planetary wheel carrier become mechanically connected with each other. 
     In order to disconnect the respective planetary gear&#39;s planetary wheel carrier and sun wheel from each other, the first and/or second electrical machine is controlled, so that torque balance is achieved in the planetary gear. When torque balance has been achieved, the coupling device is shifted, so that the sun wheel and the planetary wheel carrier are no longer mechanically connected with to each other. 
     Torque balance relates to a state where a torque acts on an internal ring gear arranged in the planetary gear, representing the product of the torque acting on the planetary wheel carrier of the planetary gear and the gear ratio of the planetary gear, while simultaneously a torque acts on the planetary gear&#39;s sun wheel, representing the product of the torque acting on the planetary wheel carrier and (1−the planetary gear&#39;s gear ratio). In the event two of the planetary gear&#39;s component parts, i.e. the sun wheel, the internal ring gear or planetary wheel carriers, are connected with a coupling device, this coupling device does not transfer any torque between the planetary gear&#39;s parts when torque balance prevails. Accordingly, the coupling device may easily be shifted and the planetary gear&#39;s component parts be disconnected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, on which: 
         FIG. 1  schematically shows a vehicle with a hybrid powertrain in a side view, arranged to be moved off according to the method, according to the present invention, 
         FIG. 2  shows a schematic side view of a hybrid powertrain, adapted for moving off of a vehicle according to the method, according to the present invention, 
         FIG. 3  shows a schematic view of a hybrid powertrain, adapted for moving off of a vehicle according to the method, according to the present invention, and 
         FIG. 4  shows a flow chart relating to the method for moving off of a vehicle according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows a schematic side view of a vehicle  1 , comprising a gearbox  2  and a combustion engine  4 , which are comprised in a hybrid powertrain  3 . The combustion engine  4  is connected to the gearbox  2 , and the gearbox  2  is further connected to the driving wheels  6  of the vehicle  1  via a propeller shaft  9 . The driving wheels  6  are equipped with brake devices  7  to brake the vehicle  1 . 
       FIG. 2  shows a schematic side view of a hybrid powertrain  3  with a gearbox  2 , comprising an input shaft  8 , a first and a second planetary gear  10  and  12 , respectively, a first and a second electrical machine  14  and  16 , respectively, a countershaft  18  and an output shaft  20 . The hybrid powertrain comprises a combustion engine  4 , connected to the gearbox  2 . The combustion engine  4  is connected with the gearbox  2  via the input shaft  8  of the gearbox. The combustion engine has an output shaft  97 . The output shaft  97  of the combustion engine  4  is connected to the input shaft of the gearbox  2 . The first planetary gear  10  has a first internal ring gear  22 , to which a first rotor  24  in the first electrical machine  14  is connected. The first planetary gear  10  also has a first sun wheel  26  and a first planetary wheel carrier  50 . The second planetary gear  12  has a second internal ring gear  28 , to which a second rotor  30  of the second electrical machine  16  is connected. The second planetary gear  12  has a second sun wheel  32  and a second planetary wheel carrier  51 . The first and the second sun wheels  26  and  32 , respectively, are coaxially arranged, which, according to the embodiment displayed, entails that a first main shaft  34  arranged on the first sun wheel  26  extends inside a second main shaft  36 , which is equipped with a central boring  38 , arranged on the second planetary wheel carrier  51 . It is also possible to arrange the first and second sun wheels  26  and  32 , respectively, and also the first main shaft  34  and the second main shaft  36 , in parallel with and next to each other. In this case, the countershaft  18  is suitably arranged between the first main shaft  34  and the second main shaft  36 , and the torque may be extracted directly from the countershaft  18 . The countershaft  18  thus constitutes, in this case, the output shaft  20 . 
     The combustion engine  4  is connected with the first planetary wheel carrier  50 , and the first planetary wheel carrier  50  is connected with the second sun wheel  32 . 
     The first electrical machine  14  is equipped with a first stator  40 , which is connected to the vehicle  1 , via a gear housing  42  surrounding the gearbox  2 . The second electrical machine  16  is equipped with a second stator  44 , which is connected to the vehicle  1 , via a gear housing  42  surrounding the gearbox  2 . The first and the second electrical machines  14  and  16  are connected to an energy storage device  46 , such as a battery, which, depending on the vehicle&#39;s  1  operating mode, operates the electrical machines  14  and  16 , respectively. At other operating modes, the electrical machines  14  and  16 , respectively, may work as generators, wherein power is supplied to the energy storage device  46 . An electronic control device  48  is connected to the energy storage device  46  and controls the supply of power to the electrical machines  14  and  16 , respectively. Preferably the energy storage device  46  is connected to the electrical machines  14  and  16 , respectively, via a switch  49 , which is connected to the control device  48 . In some operating modes, the electrical machines  14  and  16 , respectively, may also operate each other. The electrical machines  14  and  16 , respectively, may accordingly operate each other. Electric power is then led from one of the electrical machines  14 ,  16  to the second electrical machine  14 ,  16  via the switch  49 , connected to the electrical machines  14 ,  16 . Thus, it is possible to achieve a power balance between the electrical machines  14 ,  16 . Another computer  53  may also be connected to the control device  48  and the gearbox  2 . By leading electric power from the first electrical machine  14 ,  16  to the second electrical machine  14 ,  16  via a switch  49 , no electric power will be led to and from the energy storage device  46 . Thus, conditions are created for an increased life of the energy storage device  46 . 
     The first planetary gear  10  is equipped with a first planetary wheel carrier  50 , on which a first set of planetary wheels  52  is mounted. The second planetary gear  12  is equipped with a second planetary wheel carrier  51 , on which a second set of planetary wheels  54  is mounted. The first set of planetary wheels  52  interacts with the first internal ring gear  22  and the first sun wheel  26 . The second set of planetary wheels  54  interacts with the second internal ring gear  28  and the second sun wheel  32 . The input shaft  8  of the gearbox  2  is connected with the first planetary wheel carrier  50 . The first planetary wheel carrier  50  in the first planetary gear  10  is directly and fixedly connected with the second sun wheel  32  of the second planetary gear  12 . Thus, the first planetary wheel carrier  50  and the second sun wheel  32  will always have the same rotational direction and the same rotational speed. 
     A first coupling device  56  is arranged between the first sun wheel  26  and the first planetary wheel carrier  50 . By arranging the first coupling device  56  in such a way that the first sun wheel  26  and the first planetary wheel carrier  50  are connected with each other, and may therefore not rotate in relation to each other, the first planetary wheel carrier  50  and the first sun wheel  26  will rotate with equal rotational speeds. 
     A second coupling device  58  is arranged between the second sun wheel  32  and the second planetary wheel carrier  51 . By arranging the second coupling device  58  in such a way that the second sun wheel  32  and the second planetary wheel carrier  51  are connected with each other, and may therefore not rotate in relation to each other, the second planetary wheel carrier  51  and the first sun wheel  32  will rotate with equal rotational speeds. 
     Preferably, the first and second coupling devices  56 ,  58  comprise a first and a second splines-equipped coupling sleeve  55  and  57 , respectively, which is axially shiftable on a splines-equipped section on the first and second, respectively, planetary wheel carrier  50  and  51 , and on a splines-equipped section on the respective sun wheels  26  and  32 . By shifting the respective coupling sleeve  55 ,  57  so that the splines-equipped sections are connected via the respective coupling sleeves  55 ,  57 , the first planetary wheel carrier  50  and the first sun wheel  26 , as well as the second planetary wheel carrier  51  and the second sun wheel  32 , respectively, become mutually interlocked with each other and may not rotate in relation to each other. 
     The first and second coupling device  56 ,  58  according to the embodiment displayed in  FIG. 2  are arranged between the first sun wheel  26  and the first planetary wheel carrier  50 , and between the second sun wheel  28  and the second planetary wheel carrier  51 , respectively. However, it is possible to arrange an additional or alternative coupling device (not displayed) between the first internal ring gear  22  and the first planetary wheel carrier  50 , and also to arrange an additional or alternative coupling device (not displayed) between the second internal ring gear  28  and the second planetary wheel carrier  51 . 
     The first planetary wheel carrier  50  in the first planetary gear  10  is, in this embodiment, fixedly connected with the second sun wheel  32  of the second planetary gear  12 . 
     In this embodiment, a third coupling device  59  is arranged between the first ring gear  22  and the gear house  42 . By actuating the third coupling device  59 , so that the first ring gear  22  and the gear house  42  are connected with each other and accordingly may not rotate in relation to each other, a down-shift of torque will occur, that is to say an up-shift of the rotational speed from the planetary wheel carrier  50  to the first sun wheel  26  will occur. 
     In this embodiment, a fourth coupling device  61  is arranged between the second internal ring gear  28  and the gear house  42 . By actuating the fourth coupling device  61 , so that the second ring gear  28  and the gear house  42  are connected with each other, and accordingly may not rotate in relation to each other, a down-shift of torque will occur, that is to say an up-shift of the rotational speed will occur from the planetary wheel carrier  50  to the second sun wheel  32 . 
     Preferably the third and fourth coupling device  59 ,  61  comprises a third and fourth splines equipped coupling sleeve  65  and  67 , respectively, which are axially shiftable on the respective splines-equipped sections of the first and second ring gears  22  and  28 , as well as on a splines-equipped section of the gear house  42 . By shifting the respective coupling sleeves  65 ,  67  in such a way that the splines-equipped sections are connected via the respective coupling sleeves  65 ,  67 , the first ring gear  22  and the gear house  42 , and the second ring gear  28  and the gear house  42 , respectively, are interlocked and may not rotate in relation to each other. 
     A transmission device  19 , which comprises a first gear pair  60 , arranged between the first planetary gear  10  and the output shaft  20  is connected to the first and the second main shaft  34 ,  36 . The first gear pair  60  comprises a first pinion gear  62  and a first cogwheel  64 , which are in engagement with each other. A second gear pair  66  is arranged between the second planetary gear  12  and the output shaft  20 . The second gear pair  66  comprises a second pinion gear  68  and a second cogwheel  70 , which are in engagement with each other. A third gear pair  72  is arranged between the first planetary gear  10  and the output shaft  20 . The third gear pair  72  comprises a third pinion gear  74  and a third cogwheel  76 , which are in engagement with each other. A fourth gear pair  78  is arranged between the second planetary gear  12  and the output shaft  20 . The fourth gear pair  78  comprises a fourth pinion gear  80  and a fourth cogwheel  82 , which are in engagement with each other. 
     On the first main shaft  34 , the first and the third pinion gears  62  and  74 , respectively, are arranged. The first and the third pinion gears  62  and  74 , respectively, are fixedly connected with the first main shaft  34 , so that they may not rotate in relation to the first main shaft  34 . On the second main shaft  36 , the second and the fourth pinion gears  68  and  80 , respectively, are arranged. The second and the fourth pinion gears  68  and  80 , respectively, are fixedly connected with the second main shaft  36 , so that they may not rotate in relation to the second main shaft  36 . 
     The countershaft  18  extends substantially in parallel with the first and the second main shaft  34  and  36 , respectively. On the countershaft  18 , the first, second, third and fourth cogwheels  64 ,  70 ,  76  and  82 , respectively, are mounted. The first pinion gear  62  engages with the first cogwheel  64 , the second pinion gear  68  engages with the second cogwheel  70 , the third pinion gear  74  engages with the third cogwheel  76  and the fourth pinion gear  80  engages with the fourth cogwheel  82 . 
     The first, second, third and fourth cogwheels  64 ,  70 ,  76  and  82 , respectively, may be individually locked with and released from the countershaft  18  with the assistance of the first, second, third and fourth coupling elements  84 ,  86 ,  88  and  90 , respectively. The coupling elements  84 ,  86 ,  88  and  90 , respectively, preferably consist of splines-equipped sections on the cogwheels  64 ,  70 ,  76  and  82 , respectively, and on the countershaft  18 , which interact with fifth and sixth coupling sleeves  83 ,  85  which engage mechanically with the splines-equipped sections of the respective first to fourth cogwheel  64 ,  70 ,  76  and  82  and of the countershaft  18 . The first and third coupling elements  84 ,  88  are preferably equipped with a common coupling sleeve  83 , and the second and fourth coupling elements  86 ,  90  are preferably equipped with a common coupling sleeve  85 . In the released state, a relative rotation may occur between the cogwheels  64 ,  70 ,  76  and  82  and of the countershaft  18 . The coupling elements  84 ,  86 ,  88  and  90 , respectively, may also consist of friction clutches. On the countershaft  18  a fifth cogwheel  92  is also arranged, which engages with a sixth cogwheel  94 , which is arranged on the output shaft  20  of the gearbox  2 . 
     The countershaft  18  is arranged between the respective first and second planetary gears  10 ,  12  and the output shaft  20 , so that the countershaft  18  is connected with the output shaft  20  via a fifth gear pair  21 , which comprises the fifth and the sixth cogwheel  92 ,  94 . The fifth cogwheel  92  is arranged so it may be connected with and disconnected from the countershaft  18  with a fifth coupling element  93 . 
     By disconnecting the fifth cogwheel  92 , which is arranged to be disconnectable from the countershaft  18 , it is possible to transfer torque from the second planetary gear  12  to the countershaft  18  via the second gear pair  66 , and to further transfer torque from the countershaft  18  to the output shaft  20  via the first gear pair  60 . Thus, a number of gear steps is obtained, wherein torque from one of the planetary gears  10 ,  12  may be transferred to the countershaft  18 , and further along from the countershaft  18  to the main shaft  34 ,  36  connected with the second planetary gear  10 ,  12 , finally to transfer torque to the output shaft  20  of the gearbox  2 . This presumes, however, that a coupling mechanism  96  arranged between the first main shaft  34  and the output shaft  20  is connected, which is described in more detail below. 
     The fifth cogwheel  92  may be locked to and released from the countershaft  18  with the assistance of a fifth coupling element  93 . The coupling element  93  preferably consists of splines-equipped sections adapted on the fifth cogwheel  92  and the countershaft  18 , which sections interact with a ninth coupling sleeve  87 , which engages mechanically with the splines-equipped sections of the fifth cogwheel  92  and the countershaft  18 . In the released state, a relative rotation may occur between the fifth cogwheel  92  and the countershaft  18 . The fifth coupling element  93  may also consist of friction clutches. 
     At a number of gearing situations, wherein the ring gears of the planetary gears  10 ,  12  are locked with the gear house  42  with the assistance of the third and fourth coupling devices  59 ,  61 , torque will be downshifted after the first planetary gear  10  and up-shifted after the second planetary gear  12 . When the torque transfer over the first main shaft  34  via the countershaft  18  decreases after the first planetary gear  10 , shafts, pinion gears and cogwheels connected thereto may be designed to be smaller, which makes the gearbox  2  more compact. A large number of gear steps may also be obtained without any need to arrange a number of additional gear pairs in the gearbox. Accordingly, the weight and cost of the gearbox  2  are also reduced. The fifth and sixth cogwheels  92  and  94  will function like a fifth gear pair  21 , transferring torque to the output shaft  20  of the gearbox  2 . 
     Torque transfer from the input shaft  8  of the gearbox  2  to the output shaft  20  of the gearbox  2  may occur via the first or the second planetary gear  10  and  12 , respectively, and the countershaft  18 . The torque transfer may also occur directly via the first planetary gear  10 , whose first sun wheel  26  is connected, via the first main shaft  34 , to the output shaft  20  of the gearbox  2  via a coupling mechanism  96 . The coupling mechanism  96  preferably comprises a splines-equipped seventh coupling sleeve  100 , which is axially shiftable on the first main shaft  34  and on the splines-equipped sections of the output shaft  20 . By shifting the seventh coupling sleeve  100 , so that the splines-equipped sections are connected via the seventh coupling sleeve  100 , the first main shaft  34  becomes locked with the output shaft  20 , which, when rotating, will therefore have the same rotational speed. By disconnecting the fifth cogwheel  92  of the fifth gear pair  21  from the countershaft  18 , torque from the second planetary gear  12  may be transferred to the countershaft  18 , and further along from the countershaft  18  to the first main shaft  34 , connected with the first planetary gear  10 , in order finally to transfer torque via the coupling mechanism  96  to the output shaft  20  of the gearbox  2 . 
     In some operating modes the gearbox  2  may operate so that one of the sun wheels  26  and  32 , respectively, are locked with the first and the second planetary wheel carrier  50  and  51 , respectively, with the help of the first and the second coupling device  56  and  58 , respectively. The first and the second main shaft  34  and  36 , respectively, then obtain the same rotational speed as the input shaft  8  of the gearbox  2 , depending on which sun wheel  26  and  32 , respectively, is locked with the respective planetary wheel carriers  50  and  51 . One or both of the electrical machines  14  and  16 , respectively, may operate as a generator to generate electric power to the energy storage device  46 . Alternatively, the electrical machine  14  and  16 , respectively, may provide a torque injection, in order to thus increase the torque in the output shaft  20 . At some operating times, the electrical machines  14  and  16 , respectively, will supply each other with electric power, independently of the energy storage device  46 . 
     In some operating modes the gearbox  2  may operate in such a way that one of the rotors  24  and  30 , respectively, of the electrical machines  14  and  16 , respectively, is locked with the gear house  42  via the respective ring gears  22  and  28 , while the second electrical machine  14  and  16 , respectively, operate as a generator to generate electric power to the energy storage device  46 , which will be explained in more detail below. The electrical machine  14  and  16 , respectively, whose respective rotor  24  and  30 , is locked with the gear house  42 , absorbs a reaction torque from the ring gear  22  and  28 , respectively, so that torque balance prevails before the locking is carried out with the help of the third and fourth coupling devices  59  and  61 , respectively. Instead of operating as a generator, the electrical machines  14  and  16 , respectively, may provide a torque injection, in order to thus increase the torque in the output shaft  20 . Torque balance comprises a substantially zero torque state on the one hand, and a counteracting torque on the other, in order for the coupling devices  59 ,  61  to be put into a state, wherein they do not transfer torque between the ring gears  22 ,  28  and the gear house  42 . 
     It is also possible that both the first and the second electrical machine  14  and  16 , respectively, generate power to the energy storage device  46 . At engine braking the driver releases the accelerator pedal (not displayed) of the vehicle  1 . The output shaft  20  of the gearbox  2  then operates one or both electrical machines  14  and  16 , respectively, while the combustion engine  4  and the electrical machines  14  and  16 , respectively, engine brake. The electrical machines  14  and  16 , respectively, in this case generate electric power, which is stored in the energy storage device  46  in the vehicle  1 . This operating state is referred to as regenerative braking. In order to facilitate more powerful braking effect the output shaft  97  of the combustion engine&#39;s  4  may be locked and thus be prevented from rotating. Thus, only one of or both the electrical machines  14  and  16 , respectively, will function as brakes and generate electric power, which is stored in the energy storage device  46 . The locking of the output shaft  97  of the combustion engine  4  may also be carried out when the vehicle must accelerate by only one or both the electrical machines  14  and  16 , respectively. If the torque of one or both of the respective electrical machines  14  and  16  overcomes the torque off the combustion engine  4 , and having regard to the gearing between them, the combustion engine  4  will not be able to resist the large torque which the respective electrical machines  14  and  16  generate, so that it becomes necessary to lock the output shaft  97  of the combustion engine&#39;s  4 . The locking of the output shaft  97  of the combustion engine  4  is preferably carried out with a locking device  102 , which is arranged between the first planetary wheel carrier  50  and the gear hosing  42 . By locking the first planetary wheel carrier  50  and the gear housing  42 , the output shaft  97  of the combustion engine  4  will also be locked, since the output shaft  97  of the combustion engines  4  is connected with the first planetary wheel carrier  50  via the input shaft  8  of the gearbox. The locking device  102  preferably comprises a splines-equipped eighth coupling sleeve  104 , which is axially shiftable on a splines-equipped section of the first planetary wheel carrier  50 , and on a splines-equipped section of the gear housing. By shifting the eight coupling sleeve  104  so that the splines-equipped sections are connected via the coupling sleeve  104 , the first planetary wheel carrier  50 , and therefore the output shaft  97  of the combustion engine  4  is prevented from rotating. 
     The control device  48  is connected to the electrical machines  14  and  16 , respectively, to control the respective electrical machines  14  and  16 , so that they, during certain operating times, use stored electric power to supply driving power to the output shaft  20  of the gearbox  2 , and during other operating times use the kinetic energy of the output shaft  20  of the gearbox  2  to extract and store electric power. The control device  48  thus detects the rotational speed and/or the torque of the output shaft  97  of the combustion engine  4  via sensors  98  arranged at the electrical machines  14  and  16 , respectively, and in the output shaft  20  of the gearbox  2 , in order thus to gather information and to control the electrical machines  14  and  16 , respectively, to operate as electric motors or generators. The control device  48  may be a computer with software suitable for this purpose. The control device  48  also controls the flow of power between the energy storage device  46  and the respective stators  40  and  44  of the electrical machines  14  and  16 , respectively. At times when the electrical machines  14  and  16 , respectively, operate as engines, stored electric power is supplied from the energy storage device  46  to the respective stators  40  and  44 . At times when the electrical machines  14  and  16  operate as generators electric power is supplied from the respective stators  40  and  44  to the energy storage device  46 . However, as stated above, the electrical machines  14  and  16 , respectively, may, during certain operating times, supply each other with electric power, independently of the energy storage device  46 . 
     The first, second, third and fourth coupling devices  56 ,  58 ,  59  and  61 , respectively, the first, second, third, fourth and fifth coupling elements  84 ,  86 ,  88 ,  90  and  93 , respectively, the coupling mechanism  96  between the first main shaft  34  and the output shaft  20 , and the locking device  102  between the first planetary wheel carrier  50  and the gear housing  42 , are connected to the control device  48  via their respective coupling sleeves. These components are preferably activated and deactivated by electric signals from the control device  48 . The coupling sleeves are preferably shifted by non-displayed power elements, such as hydraulically or pneumatically operated cylinders. It is also possible to shift the coupling sleeves with electrically powered power elements. 
     The example embodiment in  FIG. 2  shows four pinion gears  62 ,  68 ,  74  and  80 , respectively, and four cogwheels  64 ,  70 ,  76  and  82 , respectively, and two respective planetary gears  10  and  12  with associated electrical machines  14  and  16 , respectively. However, it is possible to adapt the gearbox  2  with more or fewer pinion gears and cogwheels, and with more planetary gears with associated electrical machines. 
     Below, an up-shift from the first to the highest gear will be described, wherein the gearbox  2  is arranged in a vehicle  1 . The input shaft  8  of the gearbox  2  is connected with the output shaft  97  of the combustion engine  4  of the vehicle  1 . The output shaft  20  of the gearbox  2  is connected to a driving shaft  99  in the vehicle  1 . At idling of the combustion engine  4  and when the vehicle  1  is at a standstill, the input shaft  8  of the gearbox  2  rotates at the same time as the output shaft  20  of the gearbox  2  is at a standstill. The locking device  102  is deactivated, so that the output shaft  97  of the combustion engine  4  may rotate freely. Since the input shaft  8  of the gearbox  2  rotates, the first planetary wheel carrier  50  will also rotate, which entails that the first set of planetary wheels  52  will rotate. Since the first planetary wheel carrier  50  is connected to the second sun wheel  32 , the second sun wheel  32 , and thus also the second set of planetary wheels  54 , will rotate. By not supplying power to, or extracting power from, the first and the second electrical machines  14  and  16 , respectively, the first and the second internal rings  22  and  28 , respectively, which are connected with the respective first and second rotor  24  and  30  of the electrical machines  14  and  16 , respectively, will rotate freely, so that no torque is absorbed by the respective internal rings  22  and  28 . The first, second, third and fourth coupling devices  56 ,  58 ,  59  and  61 , respectively, are disconnected and thus not actuated. Thus, no torque will be transferred from the combustion engine  4  to the respective sun wheels  26  and  32  of the planetary gears  10  and  12 . The coupling mechanism  96  between the first main shaft  34  and the output shaft  20  is disconnected, so that the first main shaft  34  and the output shaft  20  may rotate freely in relation to each other. Since the output shaft  20  of the gearbox  2  at this stage is at a standstill, the countershaft  18  is also at a standstill. In a first step the fourth cogwheel  82  and the third cogwheel  76  are connected with the countershaft  18  with the assistance of the fourth and third coupling elements  90  and  88 , respectively. The first cogwheel  64  and the second cogwheel  70  are disconnected from the countershaft  18 . Thus, the first cogwheel  64  and the second cogwheel  70  are allowed to rotate freely in relation to the countershaft  18 . The fifth cogwheel  92  of the fifth gear pair  21  is locked on the countershaft  18  with the assistance of the fifth coupling element  93 . 
     In order to start the rotation of the output shaft  20  of the gearbox  2 , with the objective of driving the vehicle  1 , the fourth pinion gear  80  and the fourth cogwheel  82  on the countershaft  18  must be brought to rotate. This is achieved by making the second planetary wheel carrier  51  rotate. When the second planetary wheel carrier rotates, the second main shaft  36  will also rotate, and thus the fourth pinion gear  80 , which is arranged on the second main shaft  36 , also rotates. The second planetary wheel carrier  51  is made to rotate by controlling the second internal ring gear  28  with the second electrical machine  16 . By activating the second electrical machine  16  and controlling the combustion engine  4  to a suitable engine speed, the vehicle  1  begins to move as the second main shaft  36  begins to rotate. When the second planetary wheel carrier  51  and the second sun wheel  32  achieve the same rotational speed, the second sun wheel  32  is locked with the second planetary wheel carrier  51  with the assistance of the second coupling device  58 . As mentioned above, the second coupling device  58  is preferably adapted in such a way that the second sun wheel  32  and the second planetary wheel carrier  51  engage mechanically with each other. Alternatively, the second coupling device  58  may be adapted as a slip brake or a multi-plate clutch which connects, in a smooth way, the second sun wheel  32  with the second planetary wheel carrier  51 . When the second sun wheel  32  is connected with the second planetary wheel carrier  51 , the second planetary wheel carrier  51  will rotate with the same rotational speed as the output shaft  97  of the combustion engine  4 . Thus, the torque generated by the combustion engine  4  is transferred to the output shaft  20  of the gearbox  2  via the fourth pinion gear  80 , the fourth cogwheel  82  on the countershaft  18 , the fifth cogwheel  92  on the countershaft  18 , and the sixth cogwheel  94  on the output shaft  20  of the gearbox  2 . The vehicle  1  will thus begin to move off and be propelled by the first gear. 
     Each of the first, second, third and fourth gear pairs  60 ,  66 ,  72 ,  78  has a gearing, which is adapted to the vehicle&#39;s  1  desired driving characteristics. According to the example embodiment displayed in  FIG. 2 , the fourth gear pair  78  has the highest gearing compared to the first, second and third gear pairs  60 ,  66 ,  72 , which results in the fourth gear pair  78  being connected when the lowest gear is engaged. The second gear pair  66  transfers, as does the fourth gear pair  78 , torque between the second main shaft  36  and the countershaft  18 , and could instead be fitted out with the highest gearing, compared with other gear pairs  60 ,  72 ,  78 , which is why in such an embodiment the second gear pair  66  could be connected when the lowest gear is engaged. 
     When the countershaft  18  is made to rotate by the fourth cogwheel  82  on the countershaft  18 , the third cogwheel  76  on the countershaft  18  will also rotate. Thus, the countershaft  18  operates the third cogwheel  76 , which in turn operates the third pinion gear  74  on the first main shaft  34 . When the first main shaft  34  rotates, the first sun wheel  26  will also rotate, and thus, depending on the rotational speed of the output shaft  97  of the combustion engine  4  and thus the rotational speed of the first planetary wheel carrier  50 , it will cause the first internal ring gear  22  and the first rotor  24  of the first electrical machine  14  to rotate. It is thus possible to allow the first electrical machine  14  to operate as a generator to supply power to the energy storage device  46 , and/or to supply power to the second electrical machine  16 . It is also possible for the second electrical machine  16  to be operated as a generator. Alternatively, the first electrical machine  14  may emit a torque injection, by way of the control device  48  controlling the first electrical machine  14  to provide a driving torque. 
     In order to shift gears from the first to the second gear, the locking between the second sun wheel  32  and the second planetary wheel carrier  51  must cease, which is achieved by way of the first electrical machine  14  being controlled in such a way that torque balance prevails in the second planetary gear  12 . Alternatively, the second electrical machine  16  is controlled in such a way that torque balance prevails in the second planetary gear  12 . Subsequently, the second coupling device  58  is controlled, so that it disconnects the second sun wheel  32  and the second planetary wheel carrier  51  from each other. The second planetary wheel carrier  51  and also the second main shaft  36  may rotate freely, which entails that the second sun wheel  32 , the second planetary wheel carrier  51  and the second main shaft  36  no longer operate the fourth pinion gear  80 , arranged on the second main shaft  36 . This assumes that the second electrical machine  16  does not operate the second ring gear  28 . The second gear is connected, by way of the control device  48  controlling the combustion engine  4 , so that a synchronous rotational speed arises between the first planetary wheel carrier  50  and the first sun wheel  26 , in order to achieve a locking between the first planetary wheel carrier  50  and the first sun wheel  26 . This is achieved by way of controlling the first coupling device  56  in such a way that the first planetary wheel carrier  50  and the first sun wheel  26  are mechanically connected with each other. Alternatively, the first coupling device  56  may be adapted as a slip brake or a multi-plate clutch which connects, in a smooth way, the first sun wheel  26  with the first planetary wheel carrier  50 . By synchronizing the control of the combustion engine  4  and the second and first electrical machine  14  and  16 , respectively, a soft and disruption-free transition from the first to the second gear may be carried out. 
     The first main shaft  34  now rotates, operated by the output shaft  97  of the combustion engine  4 , and the first main shaft  34  now operates the third pinion gear  74 . Thus, the first planetary wheel carrier  50  now operates the third pinion gear  74 , via the first sun wheel  26  and the first main shaft  34 . Since the third cogwheel  76  is in engagement with the third pinion gear  74  and is connected with the countershaft  18 , the third cogwheel  76  will operate the countershaft  18 , which in turn operates the fifth cogwheel  92  on the countershaft  18 . The fifth cogwheel  92  in turn operates the output shaft  20  of the gearbox  2  via the sixth cogwheel  94 , which is arranged on the output shaft  20  of the gearbox  2 . The vehicle  1  is now driven with the second gear engaged. 
     When the countershaft  18  is made to rotate by the third cogwheel  76 , the fourth cogwheel  82  will also rotate. Thus, the countershaft  18  operates the fourth cogwheel  82 , which in turn operates the fourth pinion gear  80  on the second main shaft  36 . When the second main shaft  36  rotates, the second planetary wheel carrier  51  will also rotate, and thus, depending on the rotational speed of the output shaft  97  of the combustion engine  4 , and thus the rotational speed in the first planetary wheel carrier  50 , it will cause the second internal ring gear  28  and the second rotor  30  of the second electrical machine  16  to rotate. It is thus possible to allow the second electrical machine  16  to operate as a generator to supply power to the energy storage device  46 , and/or to supply power to the first electrical machine  14 . The second electrical machine  16  may also emit a torque injection, by way of the control device  48  controlling the second electrical machine  16  to provide a propulsion torque. 
     In order to shift from the second gear to the third gear, the fourth cogwheel  82  on the countershaft  18  must be disconnected from the countershaft  18  with the fourth coupling element  90 , so that the fourth cogwheel  82  may rotate freely in relation to the countershaft  18 . Subsequently, the countershaft  18  is connected with the second cogwheel  70  on the countershaft  18  via the second coupling element  86 . In order to achieve a connection of the countershaft  18  and the second cogwheel  70  on the countershaft  18 , preferably the second electrical machine  16  is controlled in such a way that a synchronous rotational speed arises between the countershaft  18  and the second cogwheel  70  on the countershaft  18 . A synchronous rotational speed may be achieved by way of measuring the rotational speed in the second rotor  30  in the second electrical machine  16 , and measuring the rotational speed in the output shaft  20 . Thus, the rotational speed in the second main shaft  36  and the rotational speed in the countershaft  18  may be determined by way of given gear ratios. The rotational speed of the respective shafts  18 ,  36  is controlled, and when a synchronous rotational speed has arisen between the countershaft  18  and the second cogwheel  70 , the countershaft  18  and the second cogwheel  70  are connected with the assistance of the second coupling element  86 . 
     In order to complete the shift from a second gear to the third gear, the locking between the first sun wheel  26  and the first planetary wheel carrier  50  must cease, which is achieved by way of the first and/or the second electrical machine  14 ,  16  being controlled in such a way that torque balance prevails in the first planetary gear  10 , following which the first coupling device  56  is controlled, in such a way that it disconnects the first sun wheel  26  and the first planetary wheel carrier  50  from each other. Subsequently, the combustion engine  4  is controlled in such a way that a synchronous rotational speed arises between the second sun wheel  32  and the second planetary wheel carrier  51 , so that the second coupling device  58  may be engaged in order thus to connect the second sun wheel  32  with the second planetary wheel carrier  51 , via the coupling sleeve  57 . By synchronizing the control of the combustion engine  2  and the second and first electrical machine  14  and  16 , respectively, a soft and disruption-free transition from the second to the third gear may be carried out. 
     The third cogwheel  76  is disconnected by controlling the first electrical machine  14  in such a way that a substantially zero torque state arises between the countershaft  18  and the third cogwheel  76 . When a substantially zero torque state arises, the third cogwheel  76  is disconnected from the countershaft  18  by controlling the third coupling element  88 , so that it releases the third cogwheel  76  from the countershaft  18 . Subsequently, the first electrical machine  14  is controlled in such a way that a synchronous rotational speed arises between the countershaft  18  and the first cogwheel  64 . When a synchronous rotational speed arises, the first cogwheel  64  is connected to the countershaft  18  by way of controlling the first coupling element  84 , so that it connects the first cogwheel  64  on the countershaft  18 . A synchronous engine speed may be achieved, since the rotational speed of the first rotor  24  in the first electrical machine  14  may be determined, and the rotational speed of the output shaft  20  is measured, following which the rotational speeds of the shafts  18 ,  34  are controlled in such a way that a synchronous engine speed arises. Thus, the rotational speed of the first main shaft  34  and the rotational speed of the countershaft  18  may be determined by way of given gear ratios. 
     The second main shaft  36  now rotates with the same rotational speed as the output shaft  97  of the combustion engine  4 , and the second main shaft  36  now operates the second pinion gear  68  via the second main shaft  36 . Since the second cogwheel  70  is in engagement with the second pinion gear  68  and is connected with the countershaft  18 , the second cogwheel  70  will operate the countershaft  18 , which in turn operates the fifth cogwheel  92  on the countershaft  18 . The fifth cogwheel  92  in turn operates the output shaft  20  of the gearbox  2  via the sixth cogwheel  94 , which is arranged on the output shaft  20  of the gearbox  2 . The vehicle  1  is now driven in a third gear. 
     When the countershaft  18  is made to rotate by the second cogwheel  70  on the countershaft  18 , the first cogwheel  64  on the countershaft  18  will also rotate. Thus, the countershaft  18  operates the first cogwheel  64 , which in turn operates the first pinion gear  62  on the first main shaft  34 . When the first main shaft  34  rotates, the first sun wheel  26  will also rotate, and thus, depending on the rotational speed of the output shaft  97  of the combustion engine  4 , and thus the rotational speed of the first planetary wheel carrier  50 , it will cause the first internal ring gear  22  and the first rotor  24  of the second electrical machine  16  to rotate. It is thus possible to allow the first electrical machine  14  to operate as a generator to supply power to the energy storage device  46 , and/or to supply power to the second electrical machine  16 . Alternatively, the first electrical machine  14  may emit a torque injection, by way of the control device  48  controlling the first electrical machine  14  to provide a driving torque. 
     In order to complete the shift from the third to the fourth gear, the locking between the second sun wheel  32  and the second planetary wheel carrier  51  must cease, which is achieved by way of the first and/or the second electrical machine  14 ,  16  being controlled in such a way that torque balance is created in the second planetary gear  12 , following which the second coupling device  58  is controlled in such a way that it disconnects the second sun wheel  32  and the second planetary wheel carrier  51  from each other. Subsequently, the first ring gear  22  is decelerated, and when the first ring gear  22  is at a standstill the third coupling device  59  is controlled in such a way that the first ring gear  22  is connected and joined with the gear house  42 . By synchronizing the control of the combustion engine  4  and the second and first electrical machine  14  and  16 , respectively, a soft and disruption-free transition from a third to a fourth gear may be carried out. 
     The first main shaft  34  is now operated by the output shaft  97  of the combustion engine  4 , and the first main shaft  34  now operates the first pinion gear  62 . Since the first cogwheel  64  is in engagement with the first pinion gear  62  and is connected with the countershaft  18 , the first cogwheel  64  will operate the countershaft  18 , which in turn operates the fifth cogwheel  92  on the countershaft  18 . The fifth cogwheel  92  in turn operates the output shaft  20  of the gearbox  2  via the sixth cogwheel  94 , which is arranged on the output shaft  20  of the gearbox  2 . The vehicle  1  is now driven in a fourth gear. 
     When the countershaft  18  is made to rotate by the first cogwheel  64 , the second cogwheel  70  on the countershaft  18  will also rotate. Thus, the countershaft  18  operates the second cogwheel  70 , which in turn operates the second pinion gear  68  on the second main shaft  36 . When the second main shaft  36  rotates, the second planetary wheel carrier  51  will also rotate, and thus, depending on the rotational speed of the output shaft  97  of the combustion engine  4  and thus the rotational speed in the first planetary wheel carrier  50 , it will cause the second sun wheel  32  and the second rotor  28  of the second electrical machine  16  to rotate. It is thus possible to allow the second electrical machine  16  to operate as a generator to supply power to the energy storage device  46 , and/or to supply power to the first electrical machine  14 . Alternatively, the second electrical machine  16  may emit a torque injection, by way of the control device  48  controlling the second electrical machine  16  in order to provide an accelerating torque. 
     In order to shift from the fourth gear to the fifth gear, the first electrical machine  14  is controlled, in such a way that torque balance prevails between the first ring gear  22  and the gearbox house  42 . When torque balance prevails between the first ring gear  22  and the gear house  42 , the third coupling device  59  is controlled in such a way that the first ring gear  22  is disconnected from the gear house  42 . Subsequently, the first electrical machine  14  is controlled in such a way that a substantially zero torque state arises between the countershaft  18  and the first cogwheel  64 . When a substantially zero torque state arises between the countershaft  18  and the first cogwheel  64 , the first coupling element  84  is controlled in such a way that the first cogwheel  64  is disconnected from the countershaft  18 . Thus, the fourth gear has been disengaged. In order to engage the fifth gear, the first electrical machine  14  is controlled in such a way that a synchronous rotational speed arises between the first main shaft  34  and the output shaft  20 . When a synchronous rotational speed arises between the first main shaft  34  and the output shaft  20 , the coupling mechanism  96  is controlled in such a way that the first main shaft  34  and the output shaft  20  are connected and joined with each other. Subsequently, the first electrical machine  14  is controlled in such a way that a substantially zero torque state arises between the countershaft  18  and the first cogwheel  92  of the fifth gear pair  21 . When a substantially zero torque state arises between the countershaft  18  and the fifth cogwheel  92 , the fifth coupling element  93  is controlled in such a way that the fifth cogwheel  92  is disconnected from the countershaft  18 . Subsequently, the first electrical machine  14  is controlled in such a way that a synchronous rotational speed arises between the countershaft  18  and the first cogwheel  64 . When a synchronous rotational speed arises between the countershaft  18  and the first cogwheel  64 , the coupling element  84  is controlled in such a way that the first cogwheel  64  is connected and joined with the countershaft  18 . Finally, the combustion engine  4  is controlled in such a way that the second ring gear  28  comes to a standstill in relation to the gear house  42 . When the second ring gear  28  is at a standstill, the fourth coupling device  61  is controlled in such a way that the second ring gear  28  is connected and locked with the gear house  42 . Thus, the vehicle  1  is now driven in the fifth gear. 
     When the fifth gear is engaged, torque from the combustion engine  4  will pass the first and second planetary wheel carriers  50 ,  51  and be transferred from the second main shaft  36  via the second gear pair  66  to the countershaft  18 , and further along via the first gear pair  60  to the first main shaft  34 , in order subsequently to be transferred to the output shaft  20  via the coupling mechanism  96 . 
     In order to shift from the fifth gear to the sixth gear, the second electrical machine  16  is controlled in such a way that torque balance prevails between the second ring gear  28  and the gear house  42 . When torque balance prevails between the second ring gear  28  and the gear house  42 , the fourth coupling device  61  is controlled in such a way that the second ring gear  28  is disconnected from the gear house  42 . Subsequently the combustion engine  4  is controlled in such a way that a synchronous rotational speed arises between the first sun wheel  26  and the first planetary wheel carrier  50 . When a synchronous rotational speed arises between the first sun wheel  26  and the first planetary wheel carrier  50 , the first coupling device  56  is controlled in such a way that the first sun wheel  26  is connected and joined with the first planetary wheel carrier  50 . Subsequently, the first electrical machine  16  is controlled in such a way that a substantially zero torque state arises between the countershaft  18  and the first cogwheel  64 . When a substantially zero torque state arises between the countershaft  18  and the first cogwheel  64 , the coupling element  84  is controlled in such a way that the first cogwheel  64  is disconnected from the countershaft  18 . Finally, the second electrical machine  16  is controlled in such a way that a synchronous rotational speed arises between the countershaft  18  and the third cogwheel  76 . When a synchronous rotational speed arises between the countershaft  18  and the third cogwheel  76 , the coupling element  88  is controlled in such a way that the third cogwheel  76  is connected and joined with the countershaft  18 . Thus, the vehicle  1  is now driven in the sixth gear. 
     When the sixth gear is engaged, torque from the combustion engine  4  will be transferred from the first planetary wheel carrier  50  to the first sun wheel  26 , and further along to the first main shaft  34 , in order subsequently to be transferred to the output shaft  20  via the coupling mechanism  96 . 
     In order to shift from the sixth gear to the seventh gear the first and/or the second electrical machines  14 ,  16  is controlled in such a way that torque balance prevails in the second planetary gear  12 . When torque balance prevails in the second planetary gear  12 , the first coupling device  56  is controlled in such a way that the first sun wheel  26  is disconnected from the first planetary wheel carrier  50 . Subsequently the combustion engine  4  is controlled in such a way that a synchronous rotational speed arises between the second sun wheel  32  and the second planetary wheel carrier  51 . When a synchronous rotational speed arises between the second sun wheel  32  and the second planetary wheel carrier  51 , the second coupling device  58  is controlled in such a way that the second sun wheel  32  is connected and joined with the second planetary wheel carrier  51 . Thus, the vehicle  1  is now driven in the seventh gear. 
     When the seventh gear is engaged, torque from the combustion engine  4  will pass the first planetary wheel carrier  50  and further along to the second main shaft  36 . Subsequently, torque is transferred from the second main shaft  36  via the second gear pair  66  to the countershaft  18 , and further via the third gear pair  72  to the first main shaft  34 , in order subsequently to be transferred to the output shaft  20  via the coupling mechanism  96 . 
     According to the embodiment above, the gearbox  2  comprises pinion gears  62 ,  68 ,  74 ,  80  and cogwheels  64 ,  70 ,  76 ,  82  arranged on the main shafts  34 ,  36  and the countershaft  18 , respectively, to transfer rotational speed and torque. However, it is possible to use another type of transmission, such as chain and belt drives, to transfer rotational speed and torque in the gearbox  2 . 
     The transmission device  19  has four gear pairs  60 ,  66 ,  72 ,  78  according to the example embodiment. However, the transmission device  19  may comprise any number of gear pairs. 
       FIG. 3  illustrates the hybrid powertrain  3  according to  FIG. 2  in a simplified view, where some components have been excluded in the interest of clarity. G 1  in  FIG. 3  consists of at least one gear pair connected with the first main shaft  34  and therefore with the first planetary gear  10 , and a gear pair G 2  consists of at least one gear pair connected with the second main shaft  36  and therefore with the second planetary gear  12 . These gear pairs G 1 , G 2  are also connected to the output shaft  20  via the countershaft  18 . G 1  and G 2 , respectively, may consist of one or several gear pairs. The gear pair G 1 , connected with the first planetary gear  10 , may for example consist of the first gear pair  60  and/or the third gear pair  72 , as described in  FIG. 2 . The gear pair G 2 , connected with the second planetary gear  12 , may for example consist of the second gear pair  66  and/or the fourth gear pair  78 , as described in  FIG. 2 . Further, at least one gear pair G 3 , connected with the output shaft  20  and the countershaft,  18  is displayed, which may consist of the fifth gear pair  21  described in  FIG. 2 . G 3  may consist of one or several gear pairs. 
     The at least one gear pair G 1 ,  60 ,  72 , connected with the first planetary gear  10  comprises at least one pinion gear  62 ,  74  and one cogwheel  64 ,  76  arranged in engagement with each other, which pinion gear  62 ,  74  may be arranged in such a way that it may be connected with and disconnected from the main shaft  34 , arranged with the first planetary gear  10 . The at least one cogwheel  64 ,  76  may be arranged so that it may be connected with and disconnected from the countershaft  18 . 
     The at least one gear pair G 2 ,  66 ,  78 , connected with the second planetary gear  12 , comprises at least one pinion gear  68 ,  80  and one cogwheel  70 ,  82  arranged in engagement with each other, which pinion gear  68 ,  80  may be arranged in such a way that it may be connected with and disconnected from the second main shaft  36 , arranged with the first planetary gear  12 . The at least one cogwheel  70 ,  82  may be arranged so that it may be connected with and disconnected from the countershaft  18 . 
     In  FIG. 3 , the third and fourth coupling devices  59  and  61  have been excluded. According to this embodiment of the invention, it is still possible to drive the vehicle in a number of operating modes and driving modes. As an example, the shift from one gear to another will be described. The components displayed in  FIG. 2  and  FIG. 3  are used to describe the shifting process. A gear is engaged when the first coupling device  56  is connected, and thus joins the first sun wheel  26  and a first planetary wheel carrier  50  arranged in the first planetary gear  10  with each other, while simultaneously the second coupling device  58  is disconnected, and thus disconnects the second sun wheel  32  and the second planetary wheel carrier  51 , arranged in the second planetary gear  12 , are from each other. At this gear the first main shaft  34  is operated by the output shaft  97  of the combustion engine  4  and, when needed, by the first electrical machine  10 , which results in the first main shaft  34  operating the first pinion gear  62 . Since the first cogwheel  64  is in engagement with the first pinion gear  62  and is connected with the countershaft  18  via the first coupling element  84 , the first cogwheel  64  will operate the countershaft  18 , which in turn operates the fifth cogwheel  92  on the countershaft  18 . The fifth cogwheel  92  in turn operates the output shaft  20  of the gearbox  2  via the sixth cogwheel  94 , which is arranged on the output shaft  20  of the gearbox  2 . 
     In order to shift to a next gear, the second electrical machine  16  is controlled in such a way that a propulsion torque is generated via the second main shaft  36  and via the second gear pair  66 , whereat the second cogwheel  70  of the second gear pair  66  is connected to the countershaft  18  via the second coupling element  86 . The propulsion torque further transmitted via the fifth gear pair  21  and finally to the output shaft  20 . 
     In order to disengage the first cogwheel  64  from the countershaft  18 , so that the fourth gear is disconnected, the combustion engine  4  and the first electric machine  14  are first controlled in such a way that the first cogwheel  64  is brought to a substantially zero torque state in relation to the countershaft  18 . When a substantially zero torque state has arisen, the first coupling element  84  is disengaged, so that the first cogwheel  64  is disconnected from the countershaft  18 . 
     Subsequently, the rotational speed of the first main shaft  34  is synchronized with the rotational speed of the output shaft  20 , following which the coupling mechanism  96  is controlled in such a way that it connects the first main shaft  34  with the output shaft  20 . 
     Subsequently, the combustion engine  4  and the first electrical machine  14  are controlled in such a way that the propulsion torque occurs via the first main shaft  34  and via the coupling mechanism  96 , and further along to the output shaft  20 . By reducing the propulsion torque from the second electrical machine  16 , the fifth coupling element  93  may be brought to a substantially zero torque state in relation to the countershaft  18 . When a substantially zero torque state has arisen, the fifth coupling element  93  is disengaged, so that the fifth cogwheel  92  of the fifth gear pair  21  is disconnected from the countershaft  18 . 
     Subsequently, with the help of the second electrical machine  16 , the rotational speed of the countershaft  18  is synchronized with the engine speed of the third cogwheel  76 , following which the third coupling element  88  is controlled in such a way that it connects the third cogwheel  76  with the countershaft  18 . When this connection has been completed, the propulsion torque may be shared between the combustion engine  4 , the first electrical machine  14  and the second electrical machine  16 . Subsequently, torque balance is created in the first planetary gear  10 , following which the first coupling device  56  disconnects the first planetary wheel carrier  50  and the first sun wheel  26  from each other. Finally, the second planetary wheel carrier  51  is rotational speed synchronized with the second sun wheel  32 , following which the second coupling device  58  connects the second planetary wheel carrier  51  and the second sun wheel  32  with each other. 
     As described, torque is extracted from the gearbox  2 , from the output shaft  20 . It is also possible to extract torque directly from the first or second main shaft  34 ,  36 , or directly from the countershaft  18 , which in this case constitutes the output shaft  20 . Torque may also be extracted in parallel from two or all of the three shafts  18 ,  34 ,  36  simultaneously. 
     Below embodiments for moving off the vehicle  1  are described. The third and fourth coupling devices  59  and  61  have been excluded, since they are not needed in the method to move off the vehicle  1 . 
     In order to move off the vehicle, the combustion engine  4  is first started, unless it has already been started. Subsequently, the first sun wheel  26  and the first planetary wheel carrier  50  are disconnected from each other, with the use of the first coupling device  56 , and the second sun wheel  32  and the second planetary wheel carrier  51  are disconnected from each other, with the use of the second coupling device  58 . In order to transmit torque to the output shaft  20 , gears corresponding to the third and fourth gear pairs  72 ,  78  are engaged, by way of connecting the third and fourth cogwheels  76 ,  82  to the countershaft  18 , to engage the gears. 
     The fifth cogwheel  92  of the fifth gear pair  21 , which may be arranged to be disconnectable from the countershaft  18 , is locked on the countershaft  18 . Subsequently, the first electrical machine  14  and the second electrical machine  16  are activated, so that the first electrical machine  14  rotates in the opposite direction to the second electrical machine  16 , which entails that a torque is generated in the output shaft  20 . The first electrical machine  14  is activated to exert a first torque T 1 , and the second electrical machine  16  is activated to exert a second torque T 2 , wherein the size of the first and the second torque T 1 , T 2  influence the power output P from the first and the second electrical machines  14 ,  16 . 
     The desired powertrain torque T D , and therefore the desired torque in the output shaft  20 , are created by way of a combination of torque from the first and second electrical machines  14 ,  16 , according to the equations E1 and E1′ below. At the same time, the total power consumed by the first and the second electrical machines  14 ,  16  will vary according to the equation E2 below. A given torque may thus be produced with different total power consumptions. If a certain power consumption is desired, the two equations are combined, wherein the torque from the first and the second electrical machines  14 ,  16  is obtained from the solution of the two equations E1 and E2, and E1′ and E2, respectively. 
     In cases where the gear pair G 3 , which is connected with the countershaft  18  and the output shaft  20 , is connected and locked on the countershaft  18 , and a coupling mechanism  96 , arranged between the first main shaft  34  and the output shaft  20  is open, the torque T D  desired in the output shaft  20  of the gearbox, also referred to as the powertrain torque, may be obtained through a combination of torque from the first and the second electrical machines  14 ,  16 , according to the equation E1 below: 
     
       
         
           
             
               
                 
                   
                     T 
                     D 
                   
                   = 
                   
                     
                       
                         - 
                         
                           T 
                           1 
                         
                       
                       ⁢ 
                       
                         K 
                         1 
                       
                       ⁢ 
                       
                         1 
                         
                           
                             G 
                             1 
                           
                           ⁢ 
                           
                             G 
                             3 
                           
                         
                       
                     
                     + 
                     
                       
                         T 
                         2 
                       
                       ⁢ 
                       
                         K 
                         2 
                       
                       ⁢ 
                       
                         1 
                         
                           
                             G 
                             2 
                           
                           ⁢ 
                           
                             G 
                             3 
                           
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   E1 
                   ] 
                 
               
             
           
         
       
     
     where T 1  is the torque that the first electrical machine  14  emits and T 2  is the torque emitted by the second electrical machine  16 . K 1  and K 2  are constants, which are determined by the number of cogs on the component parts of the respective planetary gears  10 ,  12 . G 1  is the gear ratio between the first main shaft  34  and the countershaft  18 , G 2  is the gear ratio between the second main shaft  36  and the countershaft  18 , and G 3  is the gear ratio between the countershaft  18  and the output shaft  20 , for the selected connected gear pairs. 
     In cases where the gear pair G 3 , which is connected with the countershaft  18  and the output shaft  20 , is disconnected from the countershaft  18 , and the coupling mechanism  96  is locked and thus connects the first main shaft  34  and the output shaft  20 , the torque T D  in the output shaft  20  of the gearbox is determined by the equation E1′ below: 
     
       
         
           
             
               
                 
                   
                     T 
                     D 
                   
                   = 
                   
                     
                       
                         - 
                         
                           T 
                           1 
                         
                       
                       ⁢ 
                       
                         K 
                         1 
                       
                     
                     + 
                     
                       
                         T 
                         2 
                       
                       ⁢ 
                       
                         K 
                         2 
                       
                       ⁢ 
                       
                         
                           G 
                           1 
                         
                         
                           G 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     E1 
                     ′ 
                   
                   ] 
                 
               
             
             
               
                 
                   
                     P 
                     E 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           
                             T 
                             1 
                           
                           ⁢ 
                           
                             n 
                             1 
                           
                         
                         + 
                         
                           
                             T 
                             2 
                           
                           ⁢ 
                           
                             n 
                             2 
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       
                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         π 
                       
                       60 
                     
                   
                 
               
               
                 
                   [ 
                   E2 
                   ] 
                 
               
             
           
         
       
     
     n 1  is the engine speed of the first electrical machine  14  and n 2  is the engine speed of the second electrical machine  16 . 
     When the second sun wheel  32  and the second planetary wheel carrier  51  rotate with a synchronous rotational speed, the second sun wheel  32 , arranged in the second planetary gear  12 , and a second planetary wheel carrier  51  are connected with each other, via the second coupling device  58 , so that the vehicle  1  may be operated exclusively by the combustion engine  4 . 
     Method to move off a vehicle with a hybrid drive line  3  according to the invention, comprising a combustion engine  4 ; a gearbox  2  with an input shaft  8  and an output shaft  20 , which combustion engine  4  is connected to the input shaft  8  and a first main shaft  34 ; a first planetary gear  10 , connected to the input shaft  8 ; a second planetary gear  12 , connected to the first planetary gear  10  and a second main shaft  36 ; a first electrical machine  14  connected to the first planetary gear  10 ; a second electrical machine  16 , connected to the second planetary gear  12 ; at least one gear pair G 1 ,  60 ,  72 , connected with the first main shaft  34 , and therefore with the first planetary gear  10  and the output shaft  20 ; and at least one gear pair G 2 ,  66 ,  78 , connected with the second main shaft  36 , and therefore with the second planetary gear  12  and the output shaft  20 , wherein the combustion engine  4 , via the input shaft  8 , is connected with a first planetary wheel carrier  50 , arranged in the first planetary gear  10 , and wherein the second main shaft  36  is connected with a planetary wheel carrier  51  arranged in the second planetary gear  12 . 
       FIG. 4  shows a flow chart relating to a method for moving off the vehicle  1 , comprising the steps:
         a) ensuring that the rotatable components  26 ,  50  of the first planetary gear  10  are disconnected from each other, and ensuring that the rotatable components  32 ,  51  of the second planetary gear  12  are disconnected from each other,   b) ensuring gears are engaged, corresponding to the at least one gear pair G 1 ,  60 ,  72 , which is connected with the first planetary gear  10 , and the at least one gear pair G 2 ,  66 ,  78 , which is connected with the second planetary gear  12 , and   c) activating the first electrical machine  14  and the second electrical machine  16 , so that a torque is generated in the output shaft ( 20 ).       

     Preferably, the first sun wheel  26  and a first planetary wheel carrier  50 , arranged in the first planetary gear  10 , are disconnected from each other in step a) with the use of a first coupling device  56 ; and a second sun wheel  32  and the second planetary wheel carrier  51 , arranged in the second planetary gear  12 , are disconnected from each other with the use of a second coupling device  58 . 
     The combustion engine ( 4 ) is connected with the first planetary wheel carrier  50 , which is connected with the second sun wheel  32 . 
     Preferably the at least one gear pair G 1 ,  60 ,  72 , connected with the first planetary gear  10 , comprises at least one pinion gear  62 ,  74  and cogwheel  64 ,  76  arranged to be engaged with each other, which pinion gear  62 ,  74  may be arranged to be connectible with and disconnectable from a first main shaft  34 , arranged on the first planetary gear  10 , and which cogwheel  64 ,  76  may be connected with and disconnected from a countershaft  18 . 
     The at least one gear pair G 2 ,  66 ,  78 , connected with the second planetary gear  12 , comprises at least one pinion gear  68 ,  80  and cogwheel  70 ,  82  arranged in engagement with each other, which pinion gear  68 ,  80  is arranged to be connectible with and disconnectable from a second main shaft  36 , arranged with the first planetary gear  12 , and which cogwheel  70 ,  82  is arranged to be connectible with and disconnectable from a countershaft  18 , wherein in step b) the pinion gears  62 ,  74 ,  68 ,  80  are connected to the main shafts  34 ,  36 , and the cogwheels  64 ,  76 ,  70 ,  82  are connected to the countershaft  18  to engage the gears. 
     Preferably, a fifth gear pair G 3 ,  21  is arranged between a countershaft  18  and the output shaft  20 , and the fifth gear pair G 3 ,  21  comprises a fifth cogwheel  92 , which is arranged to be disconnectable from the countershaft  18 , and in a step d) the fifth cogwheel  92  is locked on the countershaft  18 . 
     Preferably, after step c) and d), in an additional step e), a second sun wheel  32  and a second planetary wheel carrier  51 , arranged in the second planetary gear  12 , are connected with each other, with the use of a second coupling device  58 , when the second sun wheel  32  and the second planetary wheel carrier  51  rotate with a synchronous rotational speed. 
     In step c), preferably the first and the second electrical machines  14 ,  16  are activated in such a way that the first electrical machine  14  rotates in the opposite direction from the second electrical machine  16 . 
     Preferably, the first electrical machine  14  is activated in step c) to exert a first torque T 1 , and the second electrical machine  16  is activated to exert a second torque T 2 , wherein the size of the first and the second torque T 1 , T 2  influence the power output P from the first and the second electrical machines  14 ,  16  to the output shaft  20 . 
     Preferably, the first and second electrical machines  14 ,  16  are activated in step c) with electric power from the energy storage device  46 . 
     According to the invention, a computer program P, stored in the control device  48  and/or the computer  53  is provided, which may comprise procedures for moving off the vehicle  1 . 
     The program P may be stored in an executable manner, or in a compressed manner, in a memory M and/or a read/write memory R. 
     The invention also relates to a computer program product, comprising program code stored in a medium readable by a computer, in order to perform the method steps specified above, when said program code is executed in the control device  48 , or in another computer  53  connected to the control device  48 . Said program code may be stored in a non-volatile manner on said medium readable by a computer  53 . 
     The components and features specified above may, within the framework of the invention, be combined between different embodiments specified.