BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an assembly for transmitting rotating power produced by two power sources to an automotive power transmission. In particular, it pertains to an assembly for connecting the power sources through two input clutches to a powershift transmission. 
     2. Description of the Prior Art 
     Hybrid vehicle drive trains generally have two power sources, a conventional internal combustion engine, and an alternate power source, such as an electric machine, and a power transmission device. In city driving where the vehicle continuously stops and starts, the electric machine is used as a motor to start the engine and as a generator to recover kinetic energy during braking. The internal combustion engine is most suitable in highway driving, during which wheel braking and opportunities for energy recovery are infrequent, and the engine operates at its greatest efficiency. 
     In mixed driving conditions, the electric machine and combustion engine may be used together to transmit power to a transmission input shaft, depending on driving conditions and the magnitude of reserve battery capacity. 
     Integration of an electric machine into a power transmission device, specifically an automatic powershift transmission with two input clutches, which results in a compact assembly making efficient use of radial and axial dimensions that is also robustly supported and easily installed, is a desirable need in the industry. 
     SUMMARY OF THE INVENTION 
     An apparatus for transmitting power to a transmission input includes first and second sources of rotary power, first and second transmission input shafts, a clutch hub driveably connected to the first and second power sources, and first and second clutches secured to the clutch hub, for alternately closing and opening a drive connection between the first and second transmission input shafts and the clutch hub. 
     The arrangement of the elements in the apparatus is compact and has short axial length while providing robust support for centering the stator and rotor of the electric machine with high precision to improve its efficiency. 
     The first and second clutch are located axially forward of the clutch housing wall. A header provides support and limits excitation of the high voltage connection and is located axially forward of the clutch housing wall and radially outside the first and second clutch. The stator and rotor of the electric machine are located axially forward of the header and radially outside the first and second clutch. A rotor hub provides support for the rotor of the electric machine and is located axially forward of the first and second clutch and incorporates a resolver rotor. The adapter housing wall provides support for the rotor hub and is located axially forward of the rotor hub and incorporates a resolver stator. The damper/flywheel assembly is located axially forward of the adapter housing wall. 
     The arrangement of the elements in the apparatus also facilitates its easy assembly and installation. The strategic integration of the dual clutch assembly and the rotor hub assembly via a bolted joint interface allows the integrated assembly to be installed where the front support provides radial alignment and support during installation. The damper/flywheel assembly is attached to an engine separate from the rest of the apparatus which facilitates the hybrid drive train installation to be similar to a conventional manual transmission or powershift transmission installation to an engine. 
     The adapter housing functions as a sealing wall to separate the wet environment of the dual clutch assembly and stator and rotor of the electric machine from the dry environment of the damper/flywheel assembly. 
     The adapter housing flange can be easily modified to accommodate mating to various engines, which achieves the objective of a very portable overall design that does not require significant changes to the base apparatus. The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
         FIG. 1  is a cross sectional view showing the arrangement of the elements in the apparatus, including the high voltage connection, for driveably connecting an engine and an electric machine through two clutches to two transmission input shafts; and 
         FIG. 2  is a cross sectional view similar to  FIG. 1  except that the method of attaching the stator of the electric machine is shown instead of the high voltage connection; and 
         FIG. 3  is a schematic diagram of a powershift transmission. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to  FIG. 1 , a power shaft  10 , such as the crankshaft of an internal combustion engine, the shaft of a hydraulic motor, or the shaft of an electric motor, and the rotor  12  of an electric machine  14 , such as an integrated starter generator or motor, are driveably connected to, and disconnected from the input shafts  16 ,  18  of a power transmission device, such as a powershift transmission. The wheels of a motor vehicle are driveably connected alternately to the input shafts  16 ,  18  through the transmission, which can produce multiple stepped ratios of the speed of its input and output, as described below with reference to  FIG. 3 . Power shaft  10 , rotor  12  and input shafts  16 ,  18  rotate about an axis  19 . 
     A clutch housing  20  supports input shaft  18  on a bearing  22 , and a needle bearing  23  supports input shaft  16  on the inner surface of input shaft  18 . Input shaft  16  is connected at spline  24  to the hub  26  of a first clutch output cylinder  27 , and input shaft  18  is connected at spline  28  to the hub  30  of a second clutch output cylinder  31 . 
     The stator  32  of the electric machine  14  is secured by bolts  36  to the clutch housing  20 . An adapter housing  38  is secured by bolts  40  to an integral flange  42  of the clutch housing  20 . A header  33 , secured by bolts  35  to clutch housing  20 , supports and limits excitation of the high voltage connection  39  made when bolts  34  tightly secure the overlying terminals of stator  32  and connector  41  to header  33 . The rotor  12  is secured to the rotor hub  44  with a pressed ring  15 . The rotor hub  44  is supported by a bearing  43  on the adapter housing  38 . The rearward end of rotor hub  44  is connected by bolts  46  to an input cylinder  48 , which is secured to a clutch hub  50 , such that rotor hub  44 , rotor  12 , input cylinder  48 , and clutch hub  50  rotate as a unit. 
     Needle bearings  52 ,  54  support the clutch hub  50  on a front support  56 , which is secured to clutch housing  20 . A lip seal  58 , located between the adapter housing  38  and rotor hub  44 , provides a seal between the wet environment, where first and second hydraulically-actuated clutches,  60 ,  62  are located, and the dry environment, where the damper/flywheel assembly  82  and the power shaft  10  are located. 
     The dual clutch assembly that includes clutches,  60 ,  62  transmits torque from power shaft  10  and torque from rotor  12  alternately to the input shafts  16 ,  18  depending on the engaged and disengaged state of the clutches  60 ,  62 . Clutches  60 ,  62  each include respective pressure balance dam volumes  64 ,  66  containing hydraulic fluid, which volumes correct for the effect of centrifugal force on the magnitude of hydraulic pressure in the clutch actuation cylinders. 
     Front support  56  is formed with four axially spaced and radially directed fluid passages  68 , separated by five seals  70 . The passages  68 , which pass through the thickness of the front support  56  and continue through the clutch hub  50 , provides lines through which hydraulic apply pressure is communicated to the apply side of the servo piston  72  of clutch  60 , to the apply side of the servo piston  74  of clutch  62 , and to the balance dams  64 ,  66 . 
     A resolver stator  76 , located radially inward on a cylindrical flange of the adapter housing  38 , and resolver rotor  78 , located radially outward on a cylindrical flange of the rotor hub  44 , produce electronic signals representing the rotational speed and angular position of the rotor  12 . 
     The adapter housing  38  and lip seal  58  hydraulically and physically separate the dual clutch assembly from a damper/flywheel assembly  82  and the rest of the engine compartment. The damper/flywheel assembly  82  is secured at its input side by bolts  84  to the power shaft  10  and is connected at its output side by a spline  90  to rotor hub  44 . The damper/flywheel assembly  82  contains compression springs  92  arranged mutually in parallel and located in an annular damper recess  94  formed in a damper housing  95 . The springs  92  are actuated by rotational displacement of the power shaft  10  relative to the rotor hub  44 , causing the springs to compress and expand relative to a drive plate  96 , which is connected by rivets  86  to a drive hub  88 . Expansion and contraction of the springs attenuates torsional displacement and transient vibrations transmitted to rotor hub  44  from power shaft  10 . In this way, the damper/flywheel assembly  82  transmits input torque from power shaft  10  to the dual clutch assembly. 
     The damper/flywheel assembly  82  is located outside a chamber  98  that is sealed and bounded by lip seal  58 , clutch housing  20 , the integral flange  42  of the clutch housing  20 , and adapter housing  38 . The location of the damper/flywheel assembly  82  makes efficient use of the space provided, and, although the sealed volume of chamber  98  is located close to the damper/flywheel assembly  82 , chamber  98  is hydraulically isolated from it. 
     The arrangement of the elements in the apparatus shown in  FIG. 1  is assembled in steps beginning with the clutch housing  20 . Then the base transmission which includes the input shafts  16 ,  18  along with the needle bearing  23  and bearing  22  is assembled into the clutch housing  20 . Next, the header  33  and connector  41  are bolted to clutch housing  20 . The stator  32  is then secured by bolts  36  to the clutch housing  20 . The high voltage connection  39  is then made by tightly securing the overlying terminals of the stator  32  and connector  41  to the header  33  with bolts  34 . The front support  56  which includes needle bearings  52 ,  54  and seals  70  is then inserted and secured to the clutch housing  20 . Next, an integrated assembly connected by bolts  46  that includes the dual clutch assembly (containing the clutches  60 ,  62 , clutch hub  56 , input cylinder  48 , and output cylinders  27 ,  31 ) and the rotor hub assembly (containing the rotor hub  44 , bearing  43 , rotor  12 , and resolver rotor  78 ) is inserted over the front support  56 , such that clutch cylinder hubs  26  and  30  engage splines  24  and  28 , respectively. Then the adapter housing  38  which includes the lip seal  58  and the resolver stator  76  is installed and connected by bolts  40  to the integral flange  42  of the clutch housing  20 . Then the damper/flywheel assembly  82  is connected by bolts  84  to the power shaft  10  of the engine. Finally, the hybrid drive train assembly is completed by installing the engine to the adapter housing  38 , such that the drive hub  88  of the damper/flywheel assembly  82  engages the rotor hub  44  at spline  90 , and securing the engine to the adapter housing  38  with bolts. 
       FIG. 2  illustrates details of a powershift transmission  100 , which includes the first input clutch  60  for selectively connecting rotor hub  42  alternately to even-numbered gears  146  associated with a first layshaft  144 , and the second input clutch  62 , which selectively connects rotor hub  42  alternately to odd-numbered gears  147  associated with a second layshaft  149 . 
     Shaft  144  supports pinions  160 ,  162 ,  164 , which are each journalled on shaft  144 , and couplers  166 ,  168 , which are secured to shaft  144 . Pinions  160 ,  162 ,  164  are associated respectively with the second, fourth and sixth gears. Coupler  166  includes a sleeve  170 , which can be moved leftward to engage pinion  160  and driveably connect pinion  160  to shaft  144 . Coupler  168  includes a sleeve  172 , which can be moved leftward to engage pinion  162  and driveably connect pinion  162  to shaft  144  and can be moved rightward to engage pinion  164  and driveably connect pinion  164  to shaft  144 . 
     Shaft  149  supports pinions  174 ,  176 ,  178 , which are each journalled on shaft  149 , and couplers  180 ,  182 , which are secured to shaft  149 . Pinions  174 ,  176 ,  178  are associated respectively with the first, third and fifth gears. Coupler  180  includes a sleeve  184 , which can be moved leftward to engage pinion  174  and driveably connect pinion  174  to shaft  149 . Coupler  182  includes a sleeve  186 , which can be moved leftward to engage pinion  176  and driveably connect pinion  176  to shaft  149  and can be moved rightward to engage pinion  178  and driveably connect pinion  178  to shaft  149 . 
     Output  124  supports gears  188 ,  190 ,  192 , which are each secured to shaft  124 . Gear  188  meshes with pinions  160  and  174 . Gear  190  meshes with pinions  162  and  176 . Gear  192  meshes with pinions  164  and  178 . Couplers  166 ,  168 ,  180  and  182  may be synchronizers, or dog clutches or a combination of these. 
     Although operation of the transmission  100  is described with reference to forward drive only, the transmission can produce reverse drive by incorporating a reverse idler gear in one of the lower power paths and a reverse coupler for engaging reverse drive. One of the input clutches  60 ,  62  would be engaged when reverse drive operation is selected. 
     The arrangement of elements in the apparatus is compact and has short axial length while providing robust support for centering the stator  32  and rotor  12  of the electric machine  14  with high precision to improve its efficiency. The clutches  60 ,  62  are located axially forward of a rear wall of clutch housing  20 . A header  33  provides support and limits excitation of the high voltage connection  39  and is located axially forward of the rear wall of the clutch housing  20  and radially outside the clutches  60 ,  62 . The stator  32  and rotor  12  of the electric machine  14  are located axially forward of the header  33  and radially outside the clutches  60 ,  62 . The substantially aligned radial position of the header  33  and the electric machine  14  with the clutches  60 ,  62  reduces the axial length of the apparatus and facilitates cooling of the electric machine  14  and the high voltage connection  39 . A rotor hub  44  provides support for the rotor  12  of the electric machine  14  and is located axially forward of the clutches  60 ,  62  and incorporates a resolver rotor  78 , which is located axially forward of the rotor hub  44 . The adapter housing  38  provides support for the rotor hub  44  through a bearing  43  which is located axially forward of the rotor hub  44  and radially inward of the resolver rotor  78 . The adapter housing  38  is located axially forward of the rotor hub  44  and incorporates a resolver stator  76 , which is located axially rearward of the wall of the adapter housing  38 . The substantially aligned radial position of the bearing  43  with the resolver rotor  78  and the resolver stator  76  reduces the axial length of the apparatus. The lip seal  58  prevents leakage of hydraulic fluid from the chamber  98  and is located axially forward of the bearing  43  and radially inward from the wall of the adapter housing  38 . The damper/flywheel assembly  82  is located axially forward of the wall of the adapter housing  38 . 
     The arrangement of the elements in the apparatus also facilitates its easy assembly and installation. The strategic integration of the dual clutch assembly and rotor hub assembly via a bolted joint interface allows the integrated assembly to be installed where the front support  56  provides radial alignment and support during installation. The damper/flywheel assembly  82  is attached to an engine separate from the rest of the apparatus which facilitates the hybrid drive train installation to be similar to a conventional manual transmission or powershift transmission installation to an engine. 
     The adapter housing  38  functions as a sealing wall to separate the wet environment of the dual clutch assembly and electric machine  14  from the dry environment of the damper/flywheel assembly  82 . This arrangement allows the apparatus to be fully tested prior to final installation with an engine. 
     The flange of the adapter housing  38  can be easily modified to accommodate mating various engines, which makes the overall design very portable and does not require significant changes to the base apparatus. 
     In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.
An apparatus for transmitting power to a transmission input includes first and second sources of rotary power, first and second transmission input shafts, a clutch hub driveably connected to the first and second power sources, and first and second clutches secured to the clutch hub, for alternately closing and opening a drive connection between the first and second transmission input shafts and the clutch hub.