Patent Publication Number: US-9409611-B2

Title: Articulated tracked vehicle

Description:
RELATED APPLICATION DATA 
     This application is a continuation of U.S. patent application Ser. No. 13/382,653 filed Mar. 19, 2012, which was a national phase of International Application No. PCT/SE10/050782 filed Jul. 6, 2010, which claimed priority of Swedish Application No. 0950530-6 filed Jul. 7, 2009, all of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates to an articulated tracked vehicle. 
     BACKGROUND ART 
     Articulated tracked vehicles comprising a front vehicle unit and a rear vehicle unit controllably interconnected by means of a control coupling, wherein the vehicle comprises a driveline for driving the vehicle are known. The driveline comprises according to prior art a diesel engine, a gearbox connected to the diesel engine, distribution gear, and shaft gears for front and rear vehicle units, the shaft gears being arranged to distribute the power to the respective track of the vehicle. Such a driveline occupies relatively large space and is relatively heavy. 
     U.S. Pat. No. 6,880,651 B2 discloses an articulated tracked vehicle with a driveline system having a first driveline comprising a diesel engine arranged in the front vehicle unit and a second driveline comprising an electric motor/generator arranged in the rear vehicle unit. In the first driveline the diesel engine is arranged to drive a gear box which in turn is connected to a drop box arranged to drive a drive shaft being connected to the front shaft gear and rear shaft gear distributing the power to the respective track. In the second driveline the drive shaft is connected to the electric motor/generator, wherein the electric motor is arranged to be driven by means of energy from a battery pack or a capacitor such that the tracks may be driven by means of the electric motor. The first and second vehicle units may be disengaged wherein the respective vehicle unit may be driven by itself. Further the diesel engine and/or the electric motor may drive both vehicle units when the vehicle units are interconnected. A disadvantage with such a construction is that it occupies a lot of space due to among others double drivelines and is also relatively heavy. Further batteries or a corresponding energy source are required in order to energize the electric motor, which also occupies space. 
     SUMMARY OF THE INVENTION 
     The present invention provides an articulated tracked vehicle with a driveline which facilitates compact building-in in the vehicle such that space in the vehicle may be used more efficiently, and facilitates improved efficiency of the vehicle. 
     According to an embodiment the objects are achieved with an articulated tracked vehicle comprising a first vehicle unit and a second vehicle unit controllably connected by means of a control member, wherein the first vehicle unit comprises a combustion engine, wherein the combustion engine is arranged to drive a generator for electrical generation, wherein the generator is arranged to transfer power via power electronic means to at least one electric motor of at least one electric propulsion unit. 
     Hereby no mechanical transmission of power is required from the combustion engine to drive wheels of the vehicle, wherein relatively optional placement of components such as propulsion motor and power electronic means is facilitated, which in turn facilitates compact building-in in the vehicle and thus space saving such that more space for e.g. crew and/or payload is obtained. Further efficient drive of the vehicle is facilitated by utilizing electric motor in combination with the combustion engine according to above. 
     According to an embodiment of the articulated tracked vehicle said propulsion unit comprises a transmission configuration arranged to transfer power for propulsion of the vehicle. Hereby more efficient drive of the vehicle is facilitated. 
     According to an embodiment of the articulated tracked vehicle the transmission configuration comprises at least one planetary gearing. By using planetary gearing the transmission configuration may be constructed more compact which results in saving of space. 
     According to an embodiment the articulated tracked vehicle comprises an electric motor per propulsion unit. This results in a more efficient drive and a compact construction. 
     According to an embodiment the articulated tracked vehicle comprises two tracks per vehicle unit. This results in stable drive of the tracked vehicle. 
     According to an embodiment the tracked vehicle comprises an electric motor per tracked drive wheel and drive shaft. Hereby the driveline may be formed very compact which results in good space for housing of crew and/or payload. Due to the fact that one electric motor is arranged per tracked drive wheel individual control of the respective track is facilitated. Hereby pivot turn of the articulated vehicle may be provided, at least with the front vehicle unit separated. Further steering of the vehicle by means of steering of the respective track is facilitated, which results in the advantage that in case the steering of the vehicle control coupling/control member would fail, redundancy in the form of control by means of the respective track exists. 
     According to an embodiment the articulated tracked vehicle comprises an electric motor per vehicle unit. Hereby the driveline may be compactly formed which results in good saving of space for crew and/or payload. 
     According to an embodiment the articulated tracked vehicle comprises an electric motor per pair of first and second, and third and fourth drive shaft respectively. This results in compact design and consequently saving of space. 
     According to an embodiment of the articulated tracked vehicle each electric motor is arranged to drive a shaft running in the longitudinal direction of the vehicle. Hereby shaft and differential of a conventional driveline may at least to a certain extent be utilized which results in easy and cost efficient upgrading of a conventional articulated tracked vehicle. 
     According to an embodiment the articulated tracked vehicle comprises only one electric motor which is arranged in the first vehicle unit. Hereby a compact and consequently space saving solution is facilitated. 
     According to an embodiment of the articulated tracked vehicle the electric motor is arranged to drive a shaft running in the longitudinal direction of the vehicle. Hereby shaft and differential of a conventional driveline may at least to a certain extent be utilized which results in easy and cost efficient upgrading of a conventional articulated tracked vehicle. 
     According to an embodiment the articulated tracked vehicle comprises only one electric motor which is arranged in the second vehicle unit. Hereby a compact and consequently space saving solution is facilitated. 
     According to an embodiment of the articulated tracked vehicle the combustion engine is arranged to drive a shaft running in the longitudinal direction of the vehicle. Hereby shaft and differential of a conventional driveline may at least to a certain extent be utilized which results in easy and cost efficient upgrading of a conventional articulated tracked vehicle. 
     Articulated tracked vehicle according to any preceding claims, comprising an energy storage unit arranged to supply energy to said power electronic means. Hereby drive of the vehicle with the combustion engine shut off is facilitated wherein more silent drive is facilitated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be had upon the reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which: 
         FIG. 1 a    schematically illustrates an articulated tracked vehicle with a driveline according to a first embodiment of the present invention; 
         FIG. 1 b    schematically illustrates a cross section of a propulsion unit of the driveline according to  FIG. 1   a;    
         FIG. 2 a    schematically illustrates an articulated tracked vehicle with a driveline according to a second embodiment of the present invention; 
         FIG. 2 b    schematically illustrates a cross section of a propulsion unit of the driveline according to  FIG. 2   a;    
         FIG. 3  schematically illustrates an articulated tracked vehicle with a driveline according to a third embodiment of the present invention; 
         FIG. 4  schematically illustrates an articulated tracked vehicle with a driveline according to a fourth embodiment of the present invention; 
         FIG. 5  schematically illustrates an articulated tracked vehicle with a driveline according to a fifth embodiment of the present invention; and 
         FIG. 6  schematically illustrates a side view of an articulated tracked vehicle with a driveline according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 a , 2 a   ,  3 - 5  schematically illustrate an articulated tracked vehicle I; II; III; IV; V with a driveline according to different embodiments of the present invention. The tracked vehicle I; II; III; IV; V according to the embodiments below comprise a first front vehicle unit  1  and a second rear vehicle unit  2  controllably interconnected by means of control coupling/control member  3 . 
     The front vehicle unit  1  has a first track  4   a  arranged to be driven by means of a first drive wheel  5   a  connected to a first drive shaft  6   a  and a second track  4   b  arranged to be driven by means of a second drive wheel  5   b  connected to a second drive shaft  6   b . The rear vehicle unit  2  has a third track  5   c  arranged to be driven by means of a third drive wheel  5   c  connected to a third drive shaft  6   c  and a fourth track  5   d  arranged to be driven by means of a fourth drive wheel  5   d  connected to a fourth drive shaft  6   d.    
     The driveline comprises a combustion engine  10 , according to an embodiment a diesel engine, arranged to drive a generator  132  for electric generation, wherein the generator is arranged to transfer power via power electronic means  20  to at least one propulsion motor. 
     The articulated vehicle I; II; III; IV; V according to the present invention comprises according to an embodiment an electronic control unit  30  arranged to control the combustion engine  10  and power electronic means  20  for controlling propulsion motor. 
     The articulated vehicle I; II; III; IV; V according to an embodiment further comprises an actuator  40  for power request, the actuator according to an embodiment comprising a gas trigger, such as an accelerator pedal. Power request is generated on the basis of an action performed by the driver corresponding to a desire of the driver to give power to the vehicle for propulsion of the same. The actuator comprises according to a variant means for actuating drive of the respective propulsion member/electric motor, which according to a variant is provided by a control panel or the corresponding, from which a request for desired control is requested, wherein information is treated and transferred to the power electronic means  20 , wherein information/power is forwarded to the propulsion motor/electric motor. 
     The electronic control unit is signal connected to the actuator  40  for power request via a link. A driver of the vehicle may request a power to the combustion engine  10  by means of the actuator. A driver of the vehicle may request drive of propulsion motor by means of the actuator  40 . The electronic control unit  30  is arranged to receive data representing requested power from the actuator  40 . The electronic control unit  30  is arranged to communicate via a link with the power electronic means  20  wherein the requested power is compared to required power. If required power is not sufficient the electronic control unit  30  is arranged to communicate with the combustion engine  10  to increase the rotational speed for increased power, wherein increased power is sent to the generator  12  which transfers the power to the power electronics  20  for forwarding to electric motor for drive of the vehicle. 
     According to a variant of the present invention such as described in the embodiments below the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit is connected to said power electronic means  20  via a link for supplying the power electronic means with power. The energy storage unit  50  is arranged to store energy e.g. when the vehicle is braking, wherein the electric motor acts as generator such that the electric motor then generates a current which is arranged to be stored in the energy storage unit  50 . 
     By the energy storage unit  50  drive of the vehicle with the combustion engine shut off is facilitated wherein more silent drive is facilitated. 
     The energy storage unit  50  according to the variant of the present invention as described in the embodiments below may be any suitable energy storage unit  50 . According to a variant the energy storage unit is constituted by a battery or battery pack. According to an alternative variant the energy storage unit is constituted by a capacitor such as a super capacitor. 
     Herein the term “link” is referred to as a communication link which may be a physical line, such as an opto-electronic communication line, or a non-physical line, such as a wireless connection, e.g. a radio link or microwave link. 
     Herein the term “propulsion motor” is referred to as an electric motor for propulsion of the articulated tracked vehicle according to the present invention. 
     Herein the term “power electronic means” and “power electronic unit” are referred to as means/unit which among others is configured to convert alternating voltage/alternating current to continuous voltage/continuous current and vice versa, configured to transform up or down voltage, and facilitates connection to energy storage unit such as battery, capacitor or the corresponding. Further the means is configured to control rotational speed/torque of electric motors, i.e. power. The power electronic means/power electronic unit is e.g. arranged to convert alternating current from a generator to continuous current for supply of e.g. lamps, radio and the like; converting high voltage, e.g. 500 or 600 V, to lower voltage, e.g. 12, 24 or 48 V; converting low voltage, e.g. 12, 24 or 48 V, from energy storage unit to high voltage, e.g. 500 or 600 V; and transferring high voltage to electric motors. 
       FIG. 1 a    schematically illustrates an articulated tracked vehicle I with a driveline according to a first embodiment of the present invention. 
     The driveline comprises a combustion engine  10 , e.g. a diesel engine, and a generator, wherein the combustion engine  10  is arranged to drive the generator  12 . 
     The driveline further comprises a first electric propulsion unit  100   a  comprising a first propulsion motor  101  and a first transmission configuration  102  connected to the first drive shaft  6   a  and arranged to drive the first drive wheel  5   a . The driveline further comprises a second electric propulsion unit  100   b  comprising a second propulsion motor  103  and a transmission configuration  104  connected to the second drive shaft  6   b  and arranged to drive the second drive wheel  5   b . The driveline further comprises a third propulsion unit  100   c  comprising a third propulsion motor  105  and a third transmission configuration  106  connected to the third drive shaft  6   c  and arranged to dive the third drive wheel  6   c . The driveline further comprises a fourth electric propulsion unit  100   d  comprising a fourth propulsion motor  107  and a fourth transmission configuration  108  connected to the fourth drive shaft  6   d  and arranged to drive the fourth drive wheel  5   d.    
     The driveline further comprises power electronic means  20  connected to the generator  12  and arranged to receive power from the generator  12 , wherein said power electronic means  20  are arranged to transfer power to the respective propulsion motor  101 ,  103 ,  105 ,  107 . 
     The power electronic means  20  comprises a first power electronic unit  21 , a second power electronic unit  22  and a third power electronic unit  23 , the first, second and third power electronic units being connected to each other. The first power electronic unit  21  is arranged to transfer power to the first propulsion motor  101  via a first link  111 . The first power electronic unit  21  is further arranged to transfer power to the second propulsion motor  103  via a second link  112 . The second power electronic unit  22  is arranged to transfer power to the third propulsion motor  105  via a third link  113 . The second power electronic unit  22  is further arranged to transfer power to the fourth propulsion motor  107  via a fourth link  114 . 
     According to an alternative variant the first, second and third power electronic units  21 ,  22 ,  23  could be constituted by a single power electronic unit. 
     The respective propulsion motor is here constituted by an electric motor for propulsion of the articulated tracked vehicle I. In the respective electric propulsion unit  100   a ,  100   b ,  100   c ,  100   d  the respective propulsion motor  101 ,  103 ,  105 ,  107  is connected to the respective transmission configuration  102 ,  104 ,  106 ,  108 . An embodiment of an electric propulsion unit  100   a  for the first embodiment is illustrated in  FIG. 1 b   , described below. 
     The articulated tracked vehicle I further comprises the electronic control unit  30 . The electronic control unit  30  is signal connected to the combustion engine  10  for controlling the combustion engine  10  via a link. The electronic control unit  30  is further signal connected to said power electronic means  20  wherein the electronic control unit  30  is arranged to control the first power electronic unit  21  via a link, the second power electronic unit  22  via a link, and the third power electronic unit  23  via a link. The electronic control unit  30  is arranged to communicate between the combustion engine  10  and power electronic means  20 . The electronic control unit  30  is signal connected to the actuator  40  for power request via a link. 
     According to a variant the electronic control unit  30  and the power electronic means  20  could be constituted by a common unit for control and communication between combustion engine  10  and propulsion motors  101 ,  103 ,  105 ,  107 , wherein said common unit is connected to the combustion engine  10 , generator  12 , propulsion motors  101 ,  103 ,  105 ,  107  and actuator  40 . 
     Due to the fact that the combustion engine  10  is arranged to drive a generator  12  which then transfers power to said power electronics generating power to the propulsion motor no mechanical power transmission is required from the combustion engine  10  to the drive wheel  5   a ,  5   b ,  5   c ,  5   d . Hereby relatively free placement of components such as electric propulsion unit and power electronic means is facilitated. 
     According to a variant of the first embodiment the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit  50  is connected to the third power electronic unit  23  via a link  115  for supplying the power electronic means with power. Hereby drive of the vehicle I with the combustion engine  10  shut off is facilitated wherein more silent drive is facilitated. 
     By using an electric propulsion motor  101 ,  103 ,  105 ,  107  according to the first embodiment, i.e. an electric motor, per track  4   a ,  4   b ,  4   c ,  4   d , the driveline may be designed very compact which results in good space for housing of crew and/or payload. By having a propulsion motor, i.e. an electric motor, arranged per track individual control of the respective track is facilitated. Hereby a pivot turn of the articulated tracked vehicle would be obtainable. Further the vehicle I would be steerable by means of control of each track, which results in the advantage that in case of failure of the steering of the control coupling/control member  3 , redundancy in the form a steering by means of the respective track  4   a ,  4   b ,  4   c ,  4   d  exists. 
     According to a variant each propulsion motor may be individually controlled via the actuator  40 , wherein the control commands from the actuator  40  are processed in the electronic control unit  30  for transmission of power to the respective power electronic unit  21 ,  22 ,  23  of the power electronic means  20 . Hereby is facilitated to obtain an open as well as a locked differential for the entire articulated tracked vehicle I. 
       FIG. 1 b    schematically illustrates a cross section of an electric propulsion unit  100   a  as the first electric propulsion unit  100   a  of the driveline according to  FIG. 1   a.    
     The electric propulsion unit  100   a  comprises a propulsion motor  101 , i.e. an electric motor for propulsion of the articulated tracked vehicle I. The propulsion motor  101  has a rotor  101   a  arranged to rotate and a stator  101   b  being fixedly secured, e.g. in a housing of a gearbox. 
     The electric propulsion unit  100   a  further comprises a transmission configuration  102  connected to the propulsion motor  101  and arranged to transfer the rotational speed from the rotor  101   a  of the propulsion motor to the drive shaft for driving of the drive wheel. 
     The transmission configuration  102  comprises a planetary gearing  130  connected to the rotor  101   a . The planetary gearing  130  comprises a sun wheel  131 , planet wheels  132  and a ring wheel  133 . The sun wheel  131  is connected to the rotor  101   a  via a shaft such that the sun wheel  131  is arranged to be rotated by means of the rotor  101   a . The transmission configuration  102  has a high gear position H in which the entire planetary gearing  130  with the ring wheel  133  rotates with an input shaft of the planetary gearing running from the rotor  101   a  to the sun wheel  131  of the planetary gearing  130 . The planetary gearing  130  further has a low gear position L in which the ring wheel  133  is locked and the planet wheels  132  rotate with the sun wheel  131  which provides a gear reduction on the drive shaft  6   a  such that it rotates with a lower rotational speed. 
     The transmission configuration  102  also comprises a reduction gear  140  connected to the planetary gearing  130  and the drive shaft  6   a . The reduction gear  140  is arranged to reduce the rotation coming from the planetary gearing  130  such that a lower rotational speed but higher torque is provided. The reduction gear  140  comprises a sun wheel, planet wheels  142  and a ring wheel  143 . The reduction gear  140  is connected to the drive shaft  6   a  via its planet wheel  142  for providing a gear reduction. In the high gear position H of the transmission configuration the sun wheel  141  of the reduction gear  140  rotates with a higher rotational speed compared to the low gear position L. The ring wheel  143  is always locked to the housing of the gear box independent of high gear position H or low gear position L. 
     The reduction gear is a type of planetary gearing. The respective transmission configuration  102 ,  104 ,  106 ,  108  of the first embodiment is built up of planetary gearing/reduction gear  130 / 140 . Thereby a compact construction is obtained which results in more space for crew and/or payload. 
     The articulated vehicle I comprises a brake device  150  arranged to brake the drive shaft  6   a . Any suitable brake device could be used, such as wheel brake drum, electric brake, disc brake or wet brake. 
     Above a transmission configuration  102  suitable for the first embodiment of the present invention has been described. Any suitable configuration of an electric propulsion unit  100   a /transmission configuration  102  could be used though. 
       FIG. 2 a    schematically illustrates an articulated tracked vehicle II with a driveline according to a second embodiment of the present invention. 
     The driveline comprises a combustion engine  10 , e.g. a diesel engine, and a generator  12  for electric generation, wherein the combustion engine  10  is arranged to drive the generator  12 . 
     The driveline further comprises a first electric propulsion unit  200   a  comprising a first propulsion motor connected to the first and second drive shaft  6   a ,  6   b  and arranged to drive the first and second drive wheel  5   a ,  5   b . The driveline further comprises a second electric propulsion unit  200   b  comprising a second propulsion motor connected to the third and fourth drive shaft  6   c ,  6   d  and arranged to drive the third and fourth drive wheel  5   c ,  5   d . Each electric propulsion unit further comprises a transmission configuration. 
     The driveline further comprises power electronic means  20  connected to the generator  12  via a link and arranged to receive power from the generator  12 , wherein said power electronic means  20  is arranged to transfer power to the respective propulsion motor  200   a ,  200   b . The power electronic means  20  comprises a first power electronic unit  21 , a second power electronic unit  22  and a third power electronic unit  23 , the first, second and third power electronic unit being connected to each other. The first power electronic unit  21  is arranged to transfer power to the first propulsion motor  200   a  via a first link  211 . The second power electronic unit  22  is arranged to transfer power to the second propulsion motor  200   b  via a second link  212 . 
     Each propulsion motor of the respective electric propulsion unit  200   a ,  200   b  are here constituted by an electric motor for propulsion of the articulated tracked vehicle II. An embodiment of electric propulsion unit  200   a  for the second embodiment is illustrated in  FIG. 2 b   , described below. 
     The articulated vehicle II further comprises the electronic control unit  30 . The electronic control unit  30  is signal connected to the combustion engine  10  for controlling the combustion engine  10  via a link. The electronic control unit  30  is further signal connected to said power electronic means  20  wherein the electronic control unit  30  is arranged to control the first power electronic unit via a link, the second power electronic unit via a link, and the third power electronic unit via a link. The electronic control unit  30  is arranged to communicate between combustion engine  10  and power electronic means  20 . The electronic control unit  30  is signal connected to the actuator  40  for power request via a link. 
     According to a variant the electronic control unit  30  and the power electronic means  20  could be constituted by a common unit for control and communication between combustion engine  10  and propulsion motors, wherein said common unit is connected to the combustion engine  10 , generator  12 , propulsion motors and actuator  40 . 
     According to a variant of the second embodiment the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit  50  is connected to the third power electronic unit  23  via a link  215  for providing the power electronic means with power. Herby drive of the vehicle with the combustion engine  10  shut off is facilitated wherein more silent drive is facilitated. 
     By using an electric propulsion motor, i.e. electric motor for propulsion of the articulated tracked vehicle II, in accordance with the second embodiment of the respective propulsion unit  200   a ,  200   b , the driveline may be designed very compact which results in good saving of space for crew and/or payload. Further the device with electric propulsion unit  200   a ,  200   b  comprising propulsion motor and transmission configuration facilitates regulation of the output rotational speed of the respective drive shaft and thus controlling the respective vehicle. 
       FIG. 2 b    schematically illustrates a cross section of an electric propulsion unit  200   a  of the driveline according to  FIG. 2   a.    
     The electric propulsion unit  200   a  comprises a propulsion motor  201 , i.e. an electric motor for propulsion of the articulated tracked vehicle II, an electric motor  201  per pair of first and second, and third and fourth drive shaft  6   a - b ,  6   c - d  respectively. The propulsion motor  201  is arranged per pair of first and second drive wheel  5   a ,  5   b  to drive first and second drive wheels  5   a ,  5   b  (see  FIG. 2 a   ) by being arranged per pair of first and second drive shafts  6   a ,  6   b  to rotate opposite drive shafts. The propulsion motor  201  has a rotor  201   a  arranged to rotate and a stator  201   b  being fixedly secured, e.g. in a housing of a gearbox for the transmission configuration  202 . 
     The electric propulsion unit  200   a  further comprises a transmission configuration  202  connected to the propulsion motor  201  and arranged to transfer the rotational speed from the rotor  201   a  of the propulsion motor  201  to the opposite drive shafts  6   a ,  6   b  for driving of the drive wheels connected to the respective drive shaft. 
     The transmission configuration  202  comprises a planetary gearing  230  connected to the rotor  201   a . The planetary gearing comprises a son wheel  231 , planet wheel  232  and a ring wheel  233 . The sun wheel  231  is connected to the rotor  201   a  via a shaft such that the sun wheel  231  is arranged to be rotated by means of the rotor  201   a . The planetary gearing  230  has a high gear position H in which the entire planetary gearing  230  with the ring wheel  233  rotates with an input shaft of the planetary gearing  230 . The planetary gearing  230  further has a low gear position L in which the ring wheel is locked and the planet wheels  232  rotate with the sun wheel  231  which provides a gear reduction on the output shaft such that it rotates with a lower rotational speed. 
     The transmission configuration  202  also comprises a first reduction gear  240   a  connected to the first drive shaft  6   a  and a second reduction gear  240   b  connected to the second drive shaft  6   b . The transmission configuration  202  also comprises a differential  260  arranged to adapt the speed between the drive wheels. The first reduction gear  240   a  and the second reduction gear  240   b  are connected to each other via the differential  260 . 
     The first reduction gear  240   a  is further connected to the planetary gearing  230 . The first reduction gear  240   a  is arranged to reduce the rotation coming from the planetary gearing  230  such that a lower rotational speed but higher torque is obtained to the drive shaft  6   a.    
     The first reduction gear  240   a  comprises a sun wheel  241 , planet wheels  242  and a ring wheel  243 . The first reduction gear  240   a  is connected to the first drive shaft  6   a  via its planet wheels  242  for providing gear reduction. The second reduction gear  240   b  comprises a sun wheel  244 , planet wheels  245  and a ring wheel  246 . The second reduction gear  240   b  is connected to the second drive shaft  6   b  via its planet wheel  245  for provision of gear reduction. 
     The first and second reduction gear  240   a ,  240   b  are further connected to each other via a shaft  247  connected to the sun wheel  241 ,  244  of the respective reduction gear  240   a ,  240   b . The first and second reduction gear  240   a ,  240   b  are connected via the differential  260  between the respective ring wheel. 
     In the high range position H of the transmission configuration  202  the sun wheel  241 ,  244  of the first and second reduction gear  240   a ,  240   b  rotates with a higher rotational speed. The ring wheel  243 ,  246  of the first and second reduction gear  240   a ,  240   b  is always locked. The planet wheels  242 ,  245  of the first and second reduction gear  240   a ,  240   b  rotate with its respective sun wheel  241 ,  244  which results in a gear reduction on the respective drive shaft  6   a ,  6   b  such that it rotates with a lower rotational speed. The ring wheel  233  is in the low gear position L arranged to be locked to the housing of the gear box and in a high gear position H arranged to be locked to the input shaft of the sun wheel running from the rotor  201   a.    
     The electric propulsion unit  200   a  according to a variant further comprises an electric motor  270  arranged in connection to the differential  260  to regulate output rotational speed to in such a way facilitate control of the respective drive wheel and thus steering of the vehicle unit in which the electric propulsion unit  200   a  is arranged. This results in the advantage that in case the steering of the control coupling/control member would fail, redundancy in the form a steering by means of each track is possible. 
     Each reduction gear  240   a ,  240   b  is a type of planetary gearing. Due to the fact that each transmission configuration of the first embodiment is built up of a planetary gearing/reduction gear a compact construction is obtained which results in more space for crew and/or payload. 
     The articulated tracked vehicle comprises a brake device  250   a ,  250   b  for the respective drive wheel arranged to brake the respective drive shaft  6   a ,  6   b . Any suitable brake device could be used, such as brake drum, electric brake, disc brake or wet brake. 
     Above a transmission configuration  202  suitable for the second embodiment of the present invention has been described. Any suitable configuration of electric propulsion unit/transmission configuration could be used though. 
       FIG. 3  schematically illustrates an articulated tracked vehicle III with a driveline according to a third embodiment of the present invention. 
     The driveline comprises a combustion engine  10 , e.g. a diesel engine, and a generator  12 , wherein the combustion engine  10  is arranged to drive the generator  12 . 
     The driveline further comprises an electric propulsion unit  300  arranged in the front vehicle unit comprising a propulsion motor  301  arranged to drive a shaft  310  running in the longitudinal direction of the vehicle IV. The propulsion motor  301  is via the shaft  310  connected to the first and second drive shaft  6   a ,  6   b  via a first shaft gear/differential  303  and arranged to drive the first and second drive wheel  5   a ,  5   b , the first shaft gear/differential  303  being arranged in the first vehicle unit  1  in connection to the first and second drive shaft  6   a ,  6   b.    
     The propulsion motor  301  is further connected to the third and fourth drive shaft  6   c ,  6   d  via a second shaft gear/differential  304  and arranged to drive the third and fourth drive wheel  5   c ,  5   d , the second shaft gear/differential  304  being arranged in the second vehicle unit  2  in connection to the third and fourth drive shaft  6   c ,  6   d.    
     The electrical propulsion unit  300  further comprises a transmission configuration  302  connected to the propulsion motor  301 . The transmission configuration  302  is according to this variant arranged behind the propulsion motor  301 . The propulsion motor  301  and the transmission configuration  302  are arranged in connection to the shaft  310  running in the longitudinal direction of the vehicle. The shaft  310  is coupled in its front end to said first shaft gear/differential  303 . The main shaft  310  is coupled in its rear end to said second shaft gear/differential  304 . 
     The driveline further comprises power electronic means  20  connected to the generator  12  and arranged to receive power from the generator  12 , wherein said power electronic means  20  are arranged to transfer power to the propulsion motor  301 . The power electronic means  20  comprises a first power electronic unit  21  and a second power electronic unit  22 , the first and second power electronic unit  21 ,  22  being connected to each other. The first power electronic unit  21  is arranged to transfer power to the first propulsion motor  301  via a first link  311 . 
     The propulsion motor  301  is here constituted by an electric motor for propulsion of the articulated tracked vehicle III. 
     The articulated tracked vehicle further comprises the electronic control unit  30 . The electronic control unit  30  is signal connected to the combustion engine  10  for controlling the combustion engine  10  via a link. The electronic control unit  30  is further signal connected to said power electronic means  20  wherein the electronic control unit  30  is arranged to control the first power electronic unit  21  via a link and the second power electronic unit  22  via a link. The electronic control unit  30  is arranged to communicate between combustion engine  10  and power electronic means  20 . The electronic control unit  30  is signal connected to the actuator  40  for power request via a link  315 . 
     According to a variant the electronic control unit  30  and the power electronic means  20  could be constituted by a common unit for control and communication between combustion engine  10  and propulsion motors, wherein said common unit is connected to combustion engine  10 , generator  12 , propulsion motor  301  and actuator  40 . 
     According to a variant of the second embodiment the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit  50  is connected to the second power electronic unit via a link  315  for providing the power electronic means  20  with power. Hereby drive of the articulated tracked vehicle III with the combustion engine  10  shut off is facilitated wherein more silent drive is facilitated. 
     An advantage with a driveline according to the third embodiment is that propulsion motor  301 , i.e. electric motor for propulsion of the articulated tracked vehicle III, may be arranged on an existing mechanical driveline and consequently upgrading of an articulated tracked vehicle with conventional mechanical driveline may be provided relatively easy and cost efficient. 
       FIG. 4  schematically illustrates an articulated tracked vehicle IV with a driveline according to a fourth embodiment of the present invention. 
     The driveline comprises a combustion engine  10 , e.g. a diesel engine, and a generator  12 , wherein the combustion engine  10  is arranged to drive the generator  12 . 
     The driveline further comprises a first electrical propulsion unit  400   a  arranged in the front vehicle unit and comprising a first propulsion motor  401  arranged to drive a first shaft  410   a  running in the longitudinal direction of the vehicle IV. The first propulsion motor  401  is via a the first shaft  410   a  connected to the first and second drive shaft  6   a ,  6   b  via a first shaft gear/differential  405  and arranged to drive the first and second drive wheel  5   a ,  5   b , the first shaft gear/differential  405  being arranged in the first vehicle unit  1  in connection to the first and second drive shaft  6   a ,  6   b.    
     The driveline further comprises a second electric propulsion unit  400   b  arranged in the rear vehicle unit and comprising a second propulsion motor  402  arranged to drive a second shaft running in the longitudinal direction of the vehicle IV. The first propulsion motor  401  is via the second shaft  410   b  connected to the third and fourth drive shaft  6   c ,  6   d  via a second shaft gear/differential  406  and arranged to drive the third and fourth drive wheel  5   c ,  5   d , the second shaft gear/differential being arranged in the second vehicle unit  2  in connection to the third and fourth drive shaft  6   c ,  6   d.    
     The first electric propulsion unit  400   a  further comprises a first transmission configuration  402  arranged in connection to the first propulsion motor  401 . The first transmission configuration  402  is according to this variant arranged behind the first propulsion motor  401 . The first propulsion motor  401  and the first transmission configuration  402  are arranged in connection to the longitudinal first shaft  410   a . The first shaft  410   a  is coupled in its front end to said first shaft gear/differential  405  and in its rear end to said first transmission configuration  402  and first propulsion motor. The first propulsion motor is arranged to drive said first main drive shaft. 
     The second electric propulsion unit  400   b  further comprises a second transmission configuration  404  arranged in connection to the second propulsion motor  403 . The second transmission configuration  404  is according to this variant arranged behind the second propulsion motor  403 . The second propulsion motor  403  and the second transmission configuration  404  are arranged in connection to the longitudinal second shaft  410   b . The second shaft  410   b  is coupled in its front end to said second shaft gear/differential  406  and in its rear end to said second transmission configuration  404  and second propulsion motor  403 . 
     The driveline further comprises power electronic means  20  connected to the generator  12  and arranged to receive power from the generator  12 , wherein said power electronic means  20  are arranged to transfer power to the respective propulsion motor  402 ,  403 . The power electronic means comprises a first power electronic unit  21 , a second power electronic unit  22  and a third power electronic unit  23 , the first, second and third power electronic units being connected to each other. The first power electronic unit  21  is arranged to transfer power to the first propulsion motor  401  via a first link  411 . The second power electronic unit  22  is arranged to transfer power to the second propulsion motor  404  via a second link  411 . 
     Each propulsion motor  401 ,  403  is here constituted by an electric motor for propulsion of the articulated tracked vehicle IV. 
     The articulated tracked vehicle further comprises the electronic control unit  30 . The electronic control unit  30  is signal connected to the combustion engine  10  via link for controlling the combustion engine  10 . The electronic control unit  30  is further signal connected to said power electronic means  20  wherein the electronic control unit  30  is arranged to control the first power electronic unit  21  via a link, the second power electronic unit  22  via a link, and the third power electronic unit  23  via link. The electronic control unit  30  is arranged to communicate between combustion engine  10  and power electronic means  20 . The electronic control unit  30  is signal connected to the actuator  40  for power request via a link. 
     According to a variant the electronic control unit  30  and the power electronic means  20  could be constituted by a common unit for control and communication between combustion engine  10  and propulsion motors  401 ,  403 , wherein said common unit is connected to combustion engine  10 , generator  12 , propulsion motors  401 ,  403  and actuator  40 . 
     According to a variant of the second embodiment the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit  50  is connected to the third power electronic unit  23  via a link  415  for providing the power electronic means with power. Thereby drive of the articulated tracked vehicle IV with the combustion engine  10  shut off is facilitated wherein more silent drive is facilitated. 
     By arranging propulsion motor  401 ,  403 , i.e. electric motor, e.g. steering motor, in accordance with the fourth embodiment directly on the transmission configuration  402 ,  404  in the form of shaft gears a relatively simple construction which is reliable is obtained, since existing shaft gear is already tried out, and no new differential of the shaft gear needs to be constructed. Further problem with design of a new brake system is eliminated. By arranging a propulsion motor  401 ,  403  per vehicle unit in accordance with the fourth embodiment redundancy in case any of the propulsion motors would fail is obtained. The construction with an electric propulsion unit  400   a ,  400   b , i.e. propulsion motor connected to transmission configuration, in each vehicle unit facilitates a relatively compact solution such that more space for crew and/or payload is set free. 
       FIG. 5  schematically illustrates an articulated tracked vehicle V with a driveline according to a fifth embodiment of the present invention. 
     The driveline comprises a combustion engine  10 , e.g. a diesel engine, and a generator  12 , wherein the combustion engine  10  is arranged to drive the generator  12 . The generator  12  is according to this embodiment arranged in front of the combustion engine  10 . 
     The combustion engine  10  is connected to the first and second drive shaft  6   a ,  6   b  via a shaft gear/differential  505 , wherein the combustion engine  10  is arranged to drive the first and second drive wheel  5   a ,  5   b  via said shaft gear/differential. 
     A first transmission configuration is arranged in connection to the combustion engine  10 . The first transmission configuration  11  is according to this variant arranged in front of the generator  12 . The combustion engine  10  and first transmission configuration  11  constitute a mechanical propulsion unit. The combustion engine  10  and first transmission configuration  11  are arranged to drive a shaft  13  running in the longitudinal direction of the vehicle. The shaft  13  is coupled in its front end to said first drive shaft/differential  505  and in the rear end with the transmission configuration  11 /combustion engine  10 . 
     The driveline further comprises an electric propulsion unit  500  arranged in the rear vehicle unit comprising a propulsion unit  501  and second transmission configuration  502  connected to the third and fourth drive shaft  6   c ,  6   d  and arranged to drive the third and fourth drive wheel  5   c ,  5   d.    
     The driveline further comprises power electronic means  20  connected to the generator  12  and arranged to receive power from the generator  12 , wherein said power electronic means  20  are arranged to transfer power to the propulsion motor  501 . The power electronic means  20  comprises a first power electronic unit  21  and a second power electronic unit  22 , the first and second power electronic unit being connected to each other. The first power electronic unit  21  is arranged to transfer power to the propulsion motor  501  via link  511 . 
     The propulsion motor  501  of the electric propulsion unit is constituted by an electric motor for propulsion of the articulated vehicle V. 
     The articulated vehicle further comprises the electronic control unit  30 . The electronic control unit  30  is signal connected to the combustion engine  10  for controlling the combustion engine  10  via a link. The electronic control unit  30  is further signal connected to said power electronic means  20  wherein the electronic control unit  30  is arranged to control the first power electronic unit  21  via a link and the second power electronic unit  22  via a link. The electronic control unit  30  is arranged to communicate between combustion engine  10  and power electronic means  20 . The electronic control unit  30  is signal connected to the actuator  40  for power request via a link. 
     According to a variant the electronic control unit  30  and the power electronic means  20  could be constituted by a common unit for control and communication between combustion engine  10  and propulsion motor  501 , wherein said common unit is connected to combustion engine  10 , generator  12 , propulsion motor  501  and actuator  40 . 
     According to a variant of the second embodiment the driveline comprises an energy storage unit  50  arranged to store energy. The energy storage unit  50  is connected to the second power electronic unit  22  via a link  515  for providing the power electronic means  22  with power. Hereby drive of the vehicle with the combustion engine  10  shut off is facilitated wherein more silent drive is facilitated. 
     By means of the device according to the fifth embodiment mechanical drive by means of the mechanical electric propulsion unit, electric drive by means of the electric propulsion unit  500  or a combination of mechanical and electric drive by means of the mechanical and electrical propulsion unit is facilitated. 
     According to a variant the electric propulsion unit may be utilized at lower speeds and be replaced by the mechanical propulsion unit at higher speeds. The device according to the fifth embodiment facilitates construction the electrical propulsion unit  500  such that this is only used for half the maximal speed wherein lower rotational speed is obtained. Hereby no distribution box and also no cardan shaft under combustion engine, to a certain extent free placement of components which facilitates a more compact construction than conventional driveline and is consequently space saving. 
       FIG. 6  schematically illustrates a side view of an articulated tracked vehicle with a driveline according to an embodiment of the present invention. Hereby placement of driveline in accordance with the first or second embodiment is illustrated. 
     The articulated tracked vehicle I; II comprises the front vehicle unit  1  and the rear vehicle unit  2  controllably interconnected by means of the control coupling/control member  3 . In the front vehicle unit the combustion engine  10  is arranged in the front portion, the generator  12  is arranged behind the combustion engine  10  and the first, second and third power electronic units  21 ,  22 ,  23  and electronic control unit  30  behind the generator  12 . The electric propulsion units  100   a - d ;  200   a - b  are arranged in connection to the drive wheels of the respective vehicle unit  1 ,  2 . 
     Above different embodiments of an articulated tracked vehicle comprising a first vehicle unit  1  and a second vehicle unit  2  controllably connected by means of a control member  3 , the combustion engine  10  being arranged to drive a generator  12  for electric generation, wherein the generator  12  is arranged to transfer power to at least one electric motor of at least one electric propulsion unit via power electronic means  20 . Hereby no mechanical power transfer from the combustion engine to drive wheels of the vehicle is required, wherein relatively free placement of electric motor/propulsion unit is facilitated. Consequently electric motor/propulsion unit may be arranged in connection to the respective vehicle unit and consequently, depending on embodiment and design of the vehicle unit be placed in the vehicle body of first and/or second vehicle unit  1 ,  2 , outside of the vehicle body of the first and/or second vehicle unit  1 ,  2  and/or between first and second vehicle unit  1 ,  2 . 
     The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.