Abstract:
The present invention relates to a method of controlling a variable-speed transmission device of a powertrain, in particular for a hybrid vehicle, comprising a driving/receiving machine ( 20 ), a thermal engine ( 10 ), a speed variation device ( 14 ) including an engine epicyclic gear train ( 24 ) with a sun gear ( 34 ) and a crown ( 46 ), each connected to engine shaft ( 12 ) by a controlled coupling ( 26, 28 ) and to a fixed part ( 44 ) of the powertrain by a one-way automatic coupling ( 30, 32 ) and a planet gear carrier ( 52 ), and a machine epicyclic gear train ( 68 ) arranged on a shaft ( 70 ) substantially parallel to engine shaft ( 12 ) and connecting engine epicyclic gear train ( 24 ) to a track ( 94, 96 ) for motion transmission to a drive axle ( 16 ), said gear train comprising a sun gear ( 72 ), a crown ( 86 ) and a planet gear carrier ( 78 ). 
     According to the invention, the method consists in blocking sun gear ( 72 ) and crown ( 86 ) of machine epicyclic gear train ( 68 ) to provide motion of the vehicle by machine ( 20 ) alone or in combination with engine ( 10 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method of controlling a variable-speed transmission device of a powertrain, in particular for a hybrid vehicle. 
         [0002]    As it is already known, a hybrid vehicle comprises a powertrain that uses, alone or in combination, as a traction/propulsion drive means, an internal-combustion thermal engine with a variable-speed transmission device and/or a driving/receiving machine, like a rotary electric machine connected to an electric source, such as one or more batteries. 
         [0003]    This combination advantageously allows to optimize the performances of this vehicle, notably by reducing the discharge of emissions to the atmosphere as well as the fuel consumption. 
         [0004]    Thus, when the vehicle is to be driven with a high torque over a wide speed range while limiting exhaust gas and noise generation, as in an urban site, the electric machine is preferably used for driving this vehicle. 
         [0005]    On the other hand, the thermal engine is used for driving this vehicle for uses where a high driving power and a wide operating range are required. 
       BACKGROUND OF THE INVENTION 
       [0006]    As is already known from French patent application No. 2,955,165 filed by the applicant, such an automotive vehicle powertrain comprises a thermal engine with a shaft connected to a variable-speed transmission device including an engine epicyclic gear train with a sun gear and a crown connected each to the thermal engine shaft by a controlled coupling and to a fixed part of the powertrain by a one-way automatic coupling, and a planet gear carrier transmitting the speed variation to the drive axle of the vehicle through a transmission track. 
         [0007]    In order to increase the speed variation capacity when the vehicle is driven on the electric machine, the applicant has combined the variable-speed transmission device of the aforementioned document with another epicyclic gear train connecting the engine epicyclic gear train to the track for motion transmission to the drive axle of this vehicle, as described in French patent application No. 2,962,697 filed by the applicant. 
         [0008]    The applicant has further improved this transmission device notably by reducing the size thereof, more particularly the other epicyclic gear train while providing simple and effective control of this transmission. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention therefore relates to a method of controlling a variable-speed transmission device of a powertrain, in particular for a hybrid vehicle, comprising a driving/receiving machine, a thermal engine, a speed variation device including an engine epicyclic gear train with a sun gear and a crown, each connected to the engine shaft by a controlled coupling and to a fixed part of the powertrain by a one-way automatic coupling and a planet gear carrier, and a machine epicyclic gear train arranged on a shaft substantially parallel to the engine shaft and connecting the engine epicyclic gear train to a track for motion transmission to a drive axle, said gear train comprising a sun gear, a crown and a planet gear carrier, characterized in that it consists in blocking the sun gear and the crown of the machine epicyclic gear train to provide motion of the vehicle by means of the machine alone or in combination with the engine. 
         [0010]    The method can consist in providing a controlled coupling between the crown and the sun gear. 
         [0011]    The method can consist in providing a controlled coupling on the crown shaft. 
         [0012]    The method can consist in providing a controlled coupling on the toothed strip of the crown. 
         [0013]    The method can consist in providing a coupling surface on the sun gear. 
         [0014]    The method can consist in providing a coupling surface on a web carried by the sun gear. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0015]    Other features and advantages of the invention will be clear from reading the description hereafter, given by way of non limitative example, with reference to the accompanying figures wherein: 
           [0016]      FIG. 1  is a diagram showing a variable-speed transmission device of a powertrain according to the invention, and 
           [0017]      FIG. 2  diagrammatically illustrates a variant of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In  FIG. 1 , the powertrain comprises a thermal engine  10 , notably an internal-combustion engine, with an engine shaft  12 , coming from the crankshaft of this engine here, a variable-speed transmission device  14  and a drive axle  16  allowing to drive driving wheels  18  of the vehicle. 
         [0019]    The powertrain also comprises a driving/receiving machine such as an electric motor  20  with a rotor  22  that can operate either as an electric motor for driving the vehicle by being connected to an electric current source, such as batteries (not shown), or as an electric power generator and more particularly as an alternator for charging these batteries. 
         [0020]    Speed variation device  14  comprises a main epicyclic gear train  24 , referred to as engine epicyclic gear train, with two controlled couplings  26 ,  28 , here in form of friction clutches, and two one-way automatic couplings, such as free wheels  30 ,  32 . 
         [0021]    More precisely, engine epicyclic gear train  24  comprises a sun gear  34  with an externally toothed strip  36 , carried by a hollow shaft  38 , referred to as sun gear shaft, which tops engine shaft  12  while being free in rotation but fixed in translation with respect thereto. Free end  40  of this shaft rests against a bearing  42  carried by a fixed part  44  of the powertrain through free wheel  32 , referred to as sun gear free wheel, which allows rotation of the sun gear in one direction only. 
         [0022]    This gear train also comprises a crown  46  with an internally toothed strip  48  arranged concentrically to the sun gear, and connected to a hollow shaft  50 , referred to as crown shaft, surrounding sun gear hollow shaft  38  while being free in rotation, but fixed in translation with respect thereto. This crown is externally connected to fixed part  44  of the vehicle powertrain by one-way coupling  30 , referred to as crown free wheel, which allows rotation of the crown in one direction only. 
         [0023]    Of course, the two free wheels  30  and  32  are arranged in such a way that sun gear  34  and crown  46  can rotate only in the same direction, and preferably in the same direction as engine shaft  12 . 
         [0024]    Finally, this engine epicyclic gear train comprises a planet gear carrier  52  with advantageously three planet gears  54  in form of externally toothed wheels, arranged in the same angular interval with respect to one another (120° here) and meshing with the crown and the sun gear. 
         [0025]    Crown strip  48 , sun gear strip  36  and planet gears  54  are therefore arranged in the same plane, here in a vertical plane considering  FIG. 1 . 
         [0026]    These planet gears are carried each by a horizontal pin  56  while being free in rotation, but fixed in translation thereon. These planet gear pins are connected to a tubular bearing  58 , referred to as planet gear carrier bearing, surrounding sun gear shaft  38  while rotating freely thereon. 
         [0027]    The free ends of the sun gear and crown shafts carry each a controlled coupling  26  and  28 , preferably a friction clutch controlled each by a lever control  60  and  62 . 
         [0028]    Thus, clutch  26 , referred to as sun gear clutch, allows to couple the sun gear with engine shaft  12 , while the purpose of clutch  28 , referred to as crown clutch, is to couple the crown with this engine shaft. 
         [0029]    As is better visible in  FIG. 1 , planet gear carrier  52  also comprises an additional externally toothed strip  64  arranged opposite the planet gears, which is connected by meshing with an externally toothed linking strip  66  of another additional epicyclic gear train  68 , referred to as machine epicyclic gear train. 
         [0030]    This epicyclic gear train  68  is arranged on a fixed shaft  70  substantially parallel to engine shaft  12 . 
         [0031]    The machine epicyclic gear train comprises a sun gear  72  rotatingly connected to a tubular shaft  74  that surrounds fixed shaft  70  and comprises an externally toothed strip  76  carried by a flange. 
         [0032]    This sun gear cooperates with a planet gear carrier  78  comprising advantageously three planet gears  80 , in form of externally toothed wheels, carried by planet gear pins  82  and arranged in the same angular interval with respect to one another (120° here), and meshing with the teeth of drive strip  84  of crown  86  of the machine epicyclic gear train. 
         [0033]    This crown is carried by a tubular shaft  88  surrounding sun gear shaft  74 . 
         [0034]    Of course, as for engine epicyclic gear train  24 , the crown strip, the sun gear toothed strip and the planet gears are arranged in the same plane, here a vertical plane considering  FIG. 1 . 
         [0035]    As can be better seen in the figure, planet gear pins  82  are carried by a web  90  fastened to a tubular bearing  92  surrounding fixed shaft  70 . 
         [0036]    This tubular bearing also carries an externally toothed strip  94  that cooperates with another toothed wheel  96  linked to drive axle  16 , thus forming a motion transmission track between machine epicyclic gear train  68  and axle  16 . 
         [0037]    Considering the right part of  FIG. 1 , sun gear tubular shaft  74  fixedly carries a web  98  with a toothed wheel  100  that cooperates with rotor  22  of machine  20 , here through the agency of a toothed wheel  102 . 
         [0038]    Web  98  also carries a coupling surface  104  that cooperates with a controlled coupling  106  carried by tubular crown shaft  88 . 
         [0039]    This coupling thus allows to connect the crown shaft either to web  98  and therefore to rotor  22  of machine  20  and to sun gear shaft  74 , or to a fixed coupling surface  108  carried by fixed part  44  of the powertrain. 
         [0040]    Advantageously, this coupling comprises a double-acting synchromesh, referred to as machine synchromesh, with two coupling positions and a neutral position. This synchromesh is fixedly carried in rotation but freely in translation by tubular crown shaft  88  and it is intended to cooperate, under the action of a control means  110 , with either coupling surface  104  of web  98 , or with fixed part  44  of the powertrain through surface  108 . 
         [0041]    The various configurations of the powertrain assembly are now described, by way of example, when machine  20  is used as the driving machine. 
         [0042]    Both clutches  26  and  28  are therefore inactive and control means  110  is actuated so as to control the motion of the synchromesh towards position  2 . 
         [0043]    In this position, synchromesh  106  is in gear with coupling surface  104  carried by web  90 , which has the effect of blocking crown  98  with sun gear  72 . 
         [0044]    Upon rotation of machine  20 , the rotation of its rotor  22  is retransmitted to the assembly consisting of crown  86  and sun gear  72  through toothed wheels  100  and  102 . 
         [0045]    The rotation of this assembly is then transmitted to planet gear carrier  78  whose rotation drives externally toothed strip  94  to rotate. This rotation of the strip is retransmitted to toothed wheel  96  linked to drive axle  16 . 
         [0046]    In this configuration, the vehicle is driven to move only under the effect of the electric motor torque (electric mode). 
         [0047]    This operating mode can be enhanced by a power supplement provided by engine  10  through epicyclic gear train  24  (parallel hybrid mode) while maintaining synchromesh  106  in position  2 . 
         [0048]    Thus, in the configuration where both clutches  26  and  28  are in active position under the action of levers  60  and  62 , the rotation of shaft  12  of thermal engine  10  drives crown  46 , sun gear  34  and therefore planet gear carrier  52  of engine epicyclic gear train  24  to rotate. This rotation of the planet gear carrier is then transmitted to tubular shaft  88  of crown  74  of the other epicyclic gear train through strips  64  and  66 . 
         [0049]    The torque generated at the planet gear carrier of the engine epicyclic gear train thus adds up on tubular shaft  88  to the torque transmitted by electric motor  20 . 
         [0050]    In the inactive position of clutch  26  and the active position of clutch  28 , the rotation of shaft  12  of thermal engine  10  drives crown  46  to rotate, which drives planet gear carrier  52  to rotate, while the rotation of sun gear shaft  38  is blocked by free wheel  32 . This rotation of the planet gear carrier is then transmitted to tubular shaft  88  of crown  74  of machine epicyclic gear train  68  through the cooperation of strips  64  and  66 . 
         [0051]    Similarly, the torque generated at the planet gear carrier of the engine epicyclic gear train thus adds up on tubular shaft  88  to the torque transmitted by the electric motor, with this specific feature that the torque transmitted to tubular shaft  88  of the machine epicyclic gear train is different from the one where clutches  26  and  28  are in active position. 
         [0052]    In the inactive position of clutch  28  and the active position of clutch  26 , the rotation of shaft  12  of thermal engine  10  drives sun gear  34  to rotate while the rotation of crown shaft  50  is blocked by free wheel  30 . The rotation of the sun gear drives planet gear carrier  52  of gear train  24 , then tubular shaft  88  of crown  74  of machine epicyclic gear train  68  to rotate. 
         [0053]    As mentioned above, the torque generated at the planet gear carrier of the engine epicyclic gear train thus adds up on tubular shaft  88  to the torque transmitted by the electric motor. In this configuration, the torque transmitted to tubular shaft  88  of the machine epicyclic gear train is different from the one where clutches  26  and  28  are in active position and the one where clutch  26  is inactive and clutch  28  is active. 
         [0054]    The variant of  FIG. 2  differs from the example of  FIG. 1  only in a specific configuration of the machine epicyclic gear train. 
         [0055]    This epicyclic gear train  68 ′ is arranged on a fixed shaft  70 ′, free in rotation but fixed in translation and substantially parallel to engine shaft  12 , while being carried by two bearings  112  provided on fixed element  44  of the powertrain. 
         [0056]    This machine epicyclic gear train comprises a crown  86 ′ carried by a crown shaft  88 ′ surrounding shaft  70 ′ and carrying linking strip  66 ′. 
         [0057]    The gear train also comprises a planet gear carrier  78 ′ with advantageously three planet gears  80 ′ carried by planet gear pins  82 ′ and meshing with the teeth of strip  84 ′ of crown  86 ′. 
         [0058]    Planet gear pins  82 ′ are carried by a plate  114  directly connected to shaft  70 ′. 
         [0059]    The planet gears also cooperate by meshing with a sun gear  72 ′ that comprises an externally toothed strip  76 ′ carried by a flange that is fixedly mounted on sun gear shaft  74 ′ surrounding shaft  70 ′. 
         [0060]    Sun gear shaft  74 ′ carries a web  98 ′ provided with a toothed strip  116  cooperating with toothed wheel  102 ′ of rotor  22 ′ of machine  20 ′. This web also comprises a coupling surface  104 ′ that cooperates with a controlled coupling  106 ′ carried by toothed strip  84 ′ of crown  86 ′. 
         [0061]    This coupling thus allows to connect the crown either to web  98 ′ and therefore to rotor  22 ′ of machine  20 ′ and to sun gear shaft  74 ′, or to a fixed coupling surface  108 ′ carried by fixed part  44  of the powertrain. 
         [0062]    As in  FIG. 1 , this coupling advantageously comprises a double-acting synchromesh, referred to as machine synchromesh, with two coupling positions and a neutral position. This synchromesh is carried fixedly in rotation but freely in translation by crown  86 ′ and it is intended to cooperate, under the effect of a control means  110 ′, either with coupling surface  104 ′ of web  98 ′ (position  2 ), or with fixed part  44  of the powertrain (position  1 ) through surface  108 ′. 
         [0063]    Shaft  70 ′ also carries a toothed strip  94 ′ carried by a fixed web  118  on this shaft. This strip cooperates with another toothed wheel  96 ′ connected to drive axle  16 ′, thus forming a motion transmission track between machine epicyclic gear train  68  and axle  16 . 
         [0064]    As already described in connection with  FIG. 1 , this variant comprises the same operating modes: electric mode or parallel hybrid mode. 
         [0065]    This variant thus allows to have a layout of machine  20  and transmission track  94 ,  96  that can be used depending on the vehicle layouts.