Abstract:
A hybrid powertrain system for a vehicle includes an electric machine, a gear set mechanically connected with the electric machine, and a clutch mechanically coupled with at least one of a primary and secondary driveline assembly. The electric machine is configured to selectively provide motive power to at least one of the primary and secondary driveline assemblies. The gear set is configured to permit differential rotation between the primary and secondary driveline assemblies. The clutch is configured to selectively transfer torque between the primary and secondary driveline assemblies.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to hybrid automotive powertrain systems and methods of operating the same. 
         [0003]    2. Discussion 
         [0004]    Drivetrains for hybrid automotive vehicles may be configured and operated in several ways. As an example, U.S. Pat. No. 5,993,351 to Deguchi et al. discloses a first electrical motor mechanically connected to an engine and a second electrical motor mechanically connected to the engine through a clutch. Motive force is transmitted from the second electrical motor to drive wheels through a transmission. It is decided whether to release the clutch based on a detected vehicle speed and a detected required motive force. Engine output at that time is estimated. The second electrical motor is controlled such that generated torque corresponds to the estimated engine output if it is decided to release the clutch. The first electrical motor is controlled such that the torque generated by the second electrical motor is absorbed. 
         [0005]    As another example, U.S. Pat. No. 6,041,877 to Yamada et al. discloses a drive unit for a hybrid vehicle. The drive unit includes an internal combustion engine, a transmission connected to the internal combustion engine via a clutch and a primary differential gear for distributing a driving force transmitted from the transmission to primary driving wheels. The drive unit also includes a transfer connected to the primary differential gear for taking out a part of the driving force transmitted from the transmission to the primary differential gear, a pair of propeller shafts for transmitting part of the driving force from the transfer to a secondary differential gear, and an electric motor provided between the propeller shafts. The drive unit further includes a pair of clutches, each connecting the electric motor to one of the pair of propeller shafts. 
         [0006]    As yet another example, U.S. Pat. No. 6,190,282 to Deguchi et al. discloses a first electric motor connected mechanically to an engine and a second electric motor connected mechanically through a clutch to the engine. Drive force is transmitted to drive wheels through a transmission from the second electric motor. It is decided whether to connect the clutch on the basis of driving conditions. The engine is controlled so that the output of the engine meets the required force when it is decided to connect the clutch. The first electric motor functions as an electric generator such that the rotation speed of the engine reaches a target rotation speed. The clutch is connected when the engine is rotating at a target rotation speed. 
       SUMMARY 
       [0007]    A hybrid powertrain system for a vehicle includes a clutch mechanically coupled with at least one of a primary driveline assembly and secondary driveline assembly, an electric machine and a gear set mechanically connected with the electric machine. The clutch is configured to selectively transfer torque between the primary driveline assembly and secondary driveline assembly. The electric machine is configured to selectively provide motive power to at least one of the primary driveline assembly and secondary driveline assembly. The gear set is configured to permit differential rotation between the primary driveline assembly and secondary driveline assembly. 
         [0008]    A method for operating a power transfer box of an automotive hybrid powertrain includes providing motive power to at least one of a primary driveline assembly and secondary driveline assembly by converting electrical power to motive power, transferring torque between the secondary driveline assembly and primary driveline assembly via a clutch and transferring torque between the secondary driveline assembly and primary driveline assembly via a gear set. 
         [0009]    While example embodiments in accordance with the invention are illustrated and disclosed, such disclosure should not be construed to limit the invention. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram of an embodiment of a powertrain system for an automotive vehicle. 
           [0011]      FIG. 2  is a schematic diagram of the electric front/rear auxiliary drive of  FIG. 1 . 
           [0012]      FIG. 3  is a schematic diagram of another embodiment of an electric front/rear auxiliary drive. 
           [0013]      FIG. 4  is a schematic diagram of yet another embodiment of an electric front/rear auxiliary drive. 
           [0014]      FIG. 5  is a schematic diagram of still yet another embodiment of an electric front/rear auxiliary drive. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Referring now to  FIG. 1 , a hybrid electric vehicle  10  may include an engine  12 , crank machine  14 , transaxle  16  and power transfer unit  18 . The vehicle  10  may also include a front prop shaft  20 , rear prop shaft  22 , electric front/rear auxiliary drive (EFRAD)  24 , high voltage battery  26  and power electronics  28 . The vehicle  10  may further include left and right front half-shafts  30 ,  32 , rear axle assembly  34 , left and right rear half-shafts  36 ,  38  and wheel and tire assemblies  40 ,  42 ,  44 ,  46 . The operation of these elements will be described in greater detail below. 
         [0016]    In other embodiments, the vehicle  10  may have a north-south powertrain configuration and/or a fewer or greater number of electric machines. Of course, other vehicle configurations are also possible. 
         [0017]    As apparent to those of ordinary skill, elements shown adjacent to one another are mechanically coupled. As an example, the crank machine  14  is mechanically coupled with the engine  12  and transaxle  16  via, for example, suitable gearing. As another example, the rear axle assembly  34  is mechanically coupled with the left and right rear half-shafts  36 ,  38  and rear prop shaft  22  via, for example, suitable gearing. Torque may thus be transferred between the engine  12  and/or crank machine  14  and the EFRAD  24  via the transaxle  16 , power transfer unit  18  and front prop shaft  20 . Likewise, torque may be transferred between the rear axle assembly  34  and the EFRAD  24  via the rear prop shaft  22 , etc. 
         [0018]    Certain embodiments of the EFRAD  24 , as explained in detail below, may selectively transfer torque to, from and/or between the front and rear prop shafts  20 ,  22 . Certain embodiments of the EFRAD  24  may also selectively convert between motive power and electrical power. 
         [0019]    Referring now to  FIGS. 1 and 2 , an electric machine  48  includes a stator  50  and rotor  52 . The electric machine  48  may provide electrical power to, or receive electrical power from, the high voltage battery  26  via the power electronics  28 . The stator  50  is fixedly attached, e.g., bolted, with a housing (not shown) of the EFRAD  24 . The rotor  52  is rotatably located, e.g. via bearings, within a housing (not shown) and about a linking shaft  54 . The linking shaft  54  and the front prop shaft  20  are connected via a joint  55 . The rotor  52  thus rotates relative to the front prop shaft  22 . As apparent to those of ordinary skill, other arrangements and configurations are also possible. 
         [0020]    A planetary gear set  58  includes a sun gear  60 , planet gears  62  and ring gear  64 . The sun gear  60  is fixedly attached, e.g., press fit, with a leg portion  66  of the rotor  52 . The sun gear  60  thus rotates with the front prop shaft  20 . In other embodiments, any suitable gear set, e.g., parallel axis, hypoid, spiral bevel, etc., may be used. As apparent to those of ordinary skill, the use of certain gear sets may require, for example, the electric machine  48  to be repositioned within the EFRAD  24 , etc. 
         [0021]    An inner carrier  68  is fixedly attached, e.g., press fit, with the linking shaft  54 . The inner carrier  68  carries the planet gears  62  and inner clutches  70  of the clutch pack  56 . The planet gears  62  and inner clutches  70  thus rotate with the front prop shaft  20 . 
         [0022]    An outer carrier  72  is connected with the rear prop shaft  22  via a joint  74 . The outer carrier  72  carries the ring gear  64  and outer clutches  76  of the clutch pack  56 . The ring gear  64  and outer clutches  76  thus rotate with the rear prop shaft  22 . 
         [0023]    In other embodiments, inner clutches and outer clutches may be carried by any suitable component. For example, outer clutches may be carried by a leg portion of a rotor or an outer carrier. Inner clutches may be carried by a leg portion of a rotor. Other configurations are also possible. 
         [0024]    In a first mode of operation, the engine  12  produces torque and transmits it to the driveline. The electric machine  48  is disabled, and therefore provides no reaction torque to the planet gears  62  via the sun gear  60 . As a result, no torque is transferred from the planet gears  62  to the rear prop shaft  22  via the ring gear  64 . The clutch pack  56  is not compressed. As a result, no torque is transferred from the linking shaft  54  to the rear prop shaft  22  via the clutch pack  56 . Note that torque from the engine  12  is also being applied to the wheel and tire assemblies  40 ,  42  through the power transfer unit  18  and front half-shafts  30 ,  32 . 
         [0025]    In a second mode of operation, the engine  12  produces torque and transmits it to the driveline. 
         [0026]    Electrical power is produced by the electric machine  48  and is sent to the power electronics  28  to be stored in the high voltage battery  26  or used for other purposes. The electric machine  48 , therefore, applies reaction torque to the planet gears  62  via the sun gear  60 . As a result, torque is transferred from the planet gears  62  to the rear prop shaft  22  via the ring gear  64 . The clutch pack  56  is not compressed. As a result, no torque is transferred from the linking shaft  54  to the rear prop shaft  22  via the clutch pack  56 . The torque from the rear prop shaft  22  is transferred to the left and right rear half-shafts  36 ,  38  via the rear axle assembly  34  to drive the wheel and tire assemblies  44 ,  46 . 
         [0027]    In this mode of operation, the electric machine  48  behaves as a generator. If the mechanical power applied by the electric machine  48  is −x and the mechanical power applied by the front prop shaft  20  is y, the mechanical power transferred to the rear prop shaft  22  is the sum of −x and y (less any system losses.) If the electric machine  48  behaves as a motor, the mechanical power transferred to the rear prop shaft  22  is the sum of x and y (less any system losses.) 
         [0028]    In a third mode of operation, no engine torque is being transmitted to the driveline. Electrical power from the power electronics  28  is provided to the electric machine  48 . The electric machine  48 , therefore, applies torque to the planet gears  62  via the sun gear  60 , and consequently to the ring gear  64  via the planet gears  62 . As a result, torque is transferred to the front prop shaft  20  via the planet gears  62  and to the rear prop shaft  22  via the ring gear  64 . The clutch pack  56  is not compressed. As a result, no torque is transferred between the linking shaft  54  and the rear prop shaft  22  via the clutch pack  56 . The torque from the front prop shaft  20  is transferred to the left and right front half-shafts  30 ,  32  via the power transfer unit  18  to drive the wheel and tire assemblies  40 ,  42 . The torque from the rear prop shaft  22  is transferred to the left and right rear half-shafts  36 ,  38  via the rear axle assembly  34  to drive the wheel and tire assemblies  44 ,  46 . 
         [0029]    In this mode of operation, the electric machine  48  behaves as a motor. The mechanical power from the machine  48  is distributed between the front prop shaft  20  and rear prop shaft  22 , and the amount to each is a function of the driveline gear ratios, including that of the planetary gear set  58  (less any system losses.) If the electric machine  48  behaves as a generator, the mechanical power absorbed by the electric machine  48  from the front prop shaft  20  and rear prop shaft  22  is also a function of the driveline gear ratios (less any system losses.) 
         [0030]    In a fourth mode of operation, the engine  12  produces torque and transmits it to the driveline. The electric machine  48  is disabled, and therefore provides no torque to the planet gears  62  via the sun gear  60 . As a result, no torque is transferred from the planet gears  62  to the rear prop shaft  22 . The clutch pack  56  is compressed to variably transfer torque from the linking shaft  54  to the rear prop shaft  22 . The torque from the rear prop shaft  22  is transferred to the left and right rear half-shafts  36 ,  38  via the rear axle assembly  34  to drive the wheel and tire assemblies  44 ,  46 . Note that torque from the engine  12  is also being applied to the front wheel and tire assemblies  40 ,  42  through the power transfer unit  18  and front half-shafts  30 ,  32 . 
         [0031]    In a fifth mode of operation, the engine  12  produces torque and transmits it to the driveline. 
         [0000]    Electrical power is produced by the electric machine  54  and is sent to the power electronics  28  to be stored in the high voltage battery  26  or used for other purposes. The electric machine  48 , therefore, applies reaction torque to the planet gears  62  via the sun gear  60 . As a result, torque is transferred from the planet gears  62  to the rear prop shaft  22  via the ring gear  64 . The clutch pack  56  is compressed to variably transfer torque from the linking shaft  54  to the rear prop shaft  22 . The torque from the rear prop shaft  22  is transferred to the left and right rear half-shafts  36 ,  38  via the rear axle assembly  34  to drive the wheel and tire assemblies  44 ,  46 . Note that torque from the engine  12  is also being applied to the front wheel and tire assemblies  40 ,  42  through the power transfer unit  18  and the front half-shafts  30 ,  32 . 
         [0032]    In this mode of operation, the electric machine  48  behaves as a generator. The mechanical power transferred to the rear prop shaft  22  is a function of the mechanical power absorbed by the machine  48  and the amount of clutch pack  56  engagement (less any system losses.) If the electric machine  48  behaves as a motor, the mechanical power applied to the rear prop shaft  22  is a function of the mechanical power applied by the machine  48  and the amount of clutch pack  56  engagement (less any system losses.) 
         [0033]    In a sixth mode of operation, no engine torque is being transmitted to the driveline. Electrical power from the power electronics  28  is provided to the electric machine  48 . The electric machine  48 , therefore, applies torque to the planet gears  62  via the sun gear  60 , and consequently to the ring gear  64  via the planet gears  62 . As a result, torque is transferred to the front prop shaft  20  via the planet gears  62  and to the rear prop shaft  22  via the ring gear  64 . The clutch pack  56  is compressed to variably transfer torque between the linking shaft  54  to the rear prop shaft  22 , for example, to limit differentiation between the front and rear prop-shafts  20 ,  22 . The torque from the front prop shaft  20  is transferred to the left and right front half-shafts  30 ,  32  via the power transfer unit  18  to drive the wheel and tire assemblies  40 ,  42 . The torque from the rear prop shaft  22  is transferred to the left and right rear half-shafts  36 ,  38  via the rear axle assembly  34  to drive the wheel and tire assemblies  44 ,  46 . 
         [0034]    In this mode of operation, the electric machine  48  behaves as a motor. The mechanical power from the electric machine  48  is distributed between the front prop shaft  20  and rear prop shaft  22 , and the amount to each is a function of the driveline gear ratios, including that of the planetary gear set  58 , and the amount of clutch pack  56  engagement (less any system losses.) If the electric machine  48  behaves as a generator, the mechanical power absorbed by the electric machine  48  from the front prop shaft  20  and rear prop shaft  22  is also a function of the driveline gear ratios and the amount of clutch pack  56  engagement (less any system losses). 
         [0035]    The clutch pack  56  may provide variable front/rear torque biasing for regenerative braking and propulsion. As an example, the torque biasing relative to the electric machine  48  may be 50% front and 50% rear when the clutch pack  56  is fully compressed and allowing no speed differentiation between front prop shaft  20  and rear prop shaft  22 . As another example, the torque biasing relative to the electric machine  48  may be 70% front and 30% rear when the clutch pack  56  is not compressed and the planetary gear set ratio provides a 70/30 front/rear torque split. In some embodiments, variable clutch pack engagement permits variable front/rear torque biasing from 50% front and 50% rear to 70% front and 30% rear. Other biasing schemes, however, are also possible, e.g., 90/10, 40/60, etc. 
         [0036]    Referring to  FIG. 3 , numbered elements of  FIG. 3  that differ by 100 relative to the numbered elements of 2 have similar, although not necessarily identical, descriptions to the numbered elements of  FIG. 2 . In this embodiment, however, the EFRAD  124  has a configuration that is the reverse of that illustrated in  FIG. 2 . That is, the linking shaft  154  is connected with the rear prop shaft  122  via the joint  174 , and the outer carrier  172  is connected with the front prop shaft  120  via the joint  155 . 
         [0037]    As apparent to those of ordinary skill, the operation of the EFRAD  124  is similar to that of the EFRAD  24  illustrated in  FIG. 2  taking into account its reverse configuration. The EFRAD  124 , however, provides the opposite front/rear torque split relative to the EFRAD  24  illustrated in  FIG. 1 . If, for example, the EFRAD  24  illustrated in  FIG. 1  provides an arrangement with a 70/30 front/rear torque split, a reverse of that arrangement would provide a 30/70 front/rear torque split, etc. 
         [0038]    Referring to  FIG. 4 , numbered elements of  FIG. 4  that differ by 200 relative to the numbered elements of 2 have similar, although not necessarily identical, descriptions to the numbered elements of  FIG. 2 . In this embodiment, however, the outer carrier  272  does not carry the ring gear  264 . Rather, the ring gear  264  is fixedly attached, e.g., bolted, with a housing (not shown) of the EFRAD  224 . In other embodiments, any suitable gear set, e.g., parallel axis, hypoid, spiral bevel, etc., may be used. As apparent to those of ordinary skill, the use of certain gear sets may require, for example, the electric machine  248  to be repositioned within the EFRAD  224 , etc. 
         [0039]    In a first mode of operation, an engine (not shown) produces torque and transmits it to the driveline. The electric machine  248  is disabled, and therefore provides no reaction torque to the planet gears  262  via the sun gear  260 . As a result, no torque is transferred to or from the front prop shaft  220  via the planet gears  262 . The clutch pack  256  is not compressed. As a result, no torque is transferred from the linking shaft  254  to the rear prop shaft  222  via the clutch pack  256 . 
         [0040]    In a second mode of operation, the engine (not shown) produces torque and transmits it to the driveline. Electrical power is produced by the electric machine  248  and is sent to power electronics (not shown) to be stored in a high voltage battery (not shown) or used for other purposes. The electric machine  248 , therefore, applies reaction torque to the planet gears  262  via the sun gear  260 . As a result, torque produced by the engine is converted into electrical power. The clutch pack  56  is not compressed. As a result, no torque is transferred from the linking shaft  254  to the rear prop shaft  222  via the clutch pack  256 . 
         [0041]    In this mode of operation, the electric machine  248  behaves as a generator. If the electric machine  248  behaves as a motor, torque transmitted to the driveline is the sum of engine torque and electric machine torque (minus other loads and system losses). 
         [0042]    In a third mode of operation, no engine torque is being transmitted to the driveline. Electrical power from the power electronics (not shown) is provided to the electric machine  248 . The electric machine  48 , therefore, applies torque to the planet gears  262  via the sun gear  260 . As a result, torque is transferred to the front prop shaft  220  via the planet gears  262 . The clutch pack  256  is not compressed. As a result, no torque is transferred between the linking shaft  254  and the rear prop shaft  222  via the clutch pack  256 . 
         [0043]    In this mode of operation, the electric machine  248  behaves as a motor. If machine  248  behaves as a generator, mechanical power absorbed by the electric machine  248  from the front prop shaft  220  is converted to electrical power. 
         [0044]    In a fourth mode of operation, the engine (not shown) produces torque and transmits it to the driveline. The electric machine  248  is disabled, and therefore provides no torque to the planet gears  262  via the sun gear  260 . As a result, no torque is transferred to or from the front prop shaft  220  via the planet gears  262 . The clutch pack  256  is compressed to variably transfer torque from the linking shaft  254  to the rear prop shaft  222 . 
         [0045]    In a fifth mode of operation, the engine (not shown) produces torque and transmits it to the driveline. Electrical power is produced by the electric machine  254  and is sent to the power electronics (not shown) to be stored in the high voltage battery (not shown) or used for other purposes. The electric machine  248 , therefore, applies reaction torque to the planet gears  262  via the sun gear  260 . As a result, torque produced by the engine (not shown) is converted into electrical power. The clutch pack  256  is compressed to variably transfer torque from the linking shaft  254  to the rear prop shaft  222 . 
         [0046]    In this mode of operation, the electric machine  248  behaves as a generator. If the electric machine  248  behaves as a motor, torque transmitted to the driveline is the sum of engine torque and electric machine torque (minus other loads and system losses). 
         [0047]    In a sixth mode of operation, no engine torque is being transmitted to the driveline. Electrical power from the power electronics (not shown) is provided to the electric machine  248 . The electric machine  248 , therefore, applies torque to the planet gears  262  via the sun gear  260 . As a result, torque is transferred to the front prop shaft  220  via the planet gears  262 . The clutch pack  256  is compressed to variably transfer torque between the linking shaft  254  and the rear prop shaft  222 . 
         [0048]    In this mode of operation, the electric machine  248  behaves as a motor. If the electric machine  248  behaves as a generator, mechanical power absorbed by the electric machine  248  from the front prop shaft  220  and rear prop shaft  222  is converted to electrical power. 
         [0049]    The clutch pack  256  may provide variable front/rear torque biasing for regenerative braking and propulsion. As an example, the torque biasing may be 50% front and 50% rear when the clutch pack  256  is fully compressed and allowing no speed differentiation between front prop shaft  220  and rear prop shaft  222 . As another example, the torque biasing may be 100% front when the clutch pack  256  is not compressed. In some embodiments, variable clutch pack engagement allows for variable front/rear torque biasing from 50% front and 50% rear to 100% front. 
         [0050]    Referring now to  FIG. 5 , numbered elements of  FIG. 5  that differ by 100 relative to the numbered elements of 4 have similar, although not necessarily identical, descriptions to the numbered elements of  FIG. 5 . In this embodiment, however, the EFRAD  324  has a configuration that is the reverse of that illustrated in  FIG. 4 . That is, the linking shaft  354  is connected with the rear prop shaft  322  via the joint  374 , and the outer carrier  372  is connected with the front prop shaft  320  via the joint  355 . 
         [0051]    As apparent to those of ordinary skill, the operation of the EFRAD  324  is similar to that of the EFRAD  224  illustrated in  FIG. 4  taking into account its reverse configuration. The EFRAD  324 , however, provides the opposite front/rear torque split relative to the EFRAD  324  illustrated in  FIG. 4 . 
         [0052]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.