Abstract:
An assembly for transmitting power from two power sources, such as an internal combustion engine and an electric motor having a rotor, to a transmission input shaft includes a clutch hub driveably connected to the rotor, a first clutch secured to the clutch hub for alternately closing and opening a drive connection between the input shaft and clutch hub, and a second clutch secured to the clutch hub for alternately closing and opening a drive connection between the engine shaft and clutch hub.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 60/641,700, filed Jan. 6, 2005. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates generally to an assembly for transmitting power to an automotive power transmission from two power sources. In particular, it pertains to an assembly for connecting the power sources concurrently or separately to the transmission. 
     Hybrid vehicles generally have two power sources, a conventional internal combustion engine, and an alternate power source, such as an electric motor. The electric motor is used as a power source in city driving where vehicle kinetic energy can be recovered by regenerative braking, converted to electric and chemical form, and stored in a battery, from which the motor is driven. The internal combustion 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 motor 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. A compact assembly for alternately combining the output of each power source or connecting them individually to the transmission input, while making efficient use of the radial and axial dimensions of the assembly, is a long sought need in the industry. 
     SUMMARY OF THE INVENTION 
     The drive assembly of this invention supports the motor, includes multiple clutches for alternately and cooperatively connecting the engine and motor to the transmission input, provides hydraulic paths to the clutches, and incorporates a flywheel and damper assembly for isolating the engine transient vibrations. The assembly is compact and has short axial length to facilitate its being packaged in a front wheel drive vehicle, whose engine and transaxle are arranged transversely with respect to the fore and aft axis of the vehicle. The assembly is functionally robust and easy to assemble. The strategic integration and specific arrangement of the components of the assembly according to this invention help to realize these advantages. 
     An assembly, according to this invention, for transmitting power from two power sources, an internal combustion engine and an electric motor having a rotor, to a transmission input shaft includes a clutch hub driveably connected to the rotor, a first clutch secured to the clutch hub for alternately closing and opening a drive connection between the input shaft and clutch hub, and a second clutch secured to the clutch hub for alternately closing and opening a drive connection between the engine shaft and clutch hub. 
     A torsion damper having an input secured to the engine shaft and output secured to the second clutch dampens torsional displacements between the engine shaft and second clutch. A flywheel, secured to the engine shaft and second clutch, is arranged in parallel with the torsion damper and preferably is formed integrally with the damper. 
     A front support is formed with a first and second clutch-apply passages, and a first lube passage. A clutch hub is formed with a third clutch-apply passage for communicating the first clutch apply passage and a cylinder of the first clutch. A fourth clutch apply passage communicates the second clutch-apply passage and a cylinder of the second clutch. A second lube passage carries fluid lubricant from the first lube passage to the first and second clutches. 
     A seal cover is secured to a clutch housing for sealing a space containing the first and second clutches and motor within the clutch housing against passage of hydraulic fluid. The seal cover and clutch housing contain the clutches and motor in a lubricated wet space close to the transmission case interior and away from the relatively dry engine compartment. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which: 
         FIG. 1  is a cross sectional side view showing a modular arrangement of components for driveably connecting an electric motor and engine alternately or concurrently through two clutches to a transmission input shaft; and 
         FIG. 2  is a chart showing the effect of clutch state on the potential drive connections to the input shaft. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing, the engine  10  of an internal combustion engine and the rotor  12  of an electric motor  14  are driveably connected to, and disconnected from the input shaft  16  of a power transmission. The wheels of a motor vehicle are driveably connected to the input shaft  16  through the transmission, which can produce multiple stepped ratios or continuously variable ratios of the speed of its input and output. 
     A front support  18  is secured to a clutch housing  20 , and includes a sleeve-like hub  19 , which surrounds and extends axially parallel to the input shaft  16 . A rotor hub assembly  22 , supported on the front support  18  on axially spaced bushings  24 ,  26 , includes an outer cylindrical drum  27  and an inner cylindrical sleeve-like hub  28 , which surrounds and extends axially parallel to the hub  19  of the front support  18 . 
     The rotor  12  of the motor  14  is supported on the outer cylindrical drum  27  of the rotor hub assembly  22 , the stator  30  surrounds the rotor  12  and is supported on the clutch housing  20 . 
     Clutches  34 ,  36  are hydraulically actuated friction clutches. The twin clutch assembly  32  includes a disconnect clutch  34  for connecting and disconnecting the engine shaft  10  and clutch hub  76 , and a launch clutch  36  for connecting and disconnecting the clutch hub  76  and input shaft  16 . Launch clutch  36  can transmit engine torque and motor torque to the input shaft  16  separately or concurrently depending on the state of clutch  36 . Clutches  34 ,  36  include respective pressure balance volumes  29 ,  31  containing hydraulic fluid, which volumes correct for the effect of centrifugal force on the magnitude of hydraulic pressure in the clutch actuation cylinders. 
     The hub  76  of the twin clutch assembly  32  is formed with axially spaced and radially directed fluid passages  33 ,  35 ,  37 , which pass through the thickness of the hub. Passage  33  provides a line through which hydraulic apply pressure is communicated to the apply side of the cylinder of disconnect clutch  34 . Passage  35  provides a line through which hydraulic apply pressure is communicated to the apply side of the cylinder of launch clutch  36 . Passages  37  provide lines through which fluid is supplied to the balance volumes of disconnect clutch  34  and launch clutch  36 , respectively. 
     Hydraulic passages  38 ,  40 , and  42  are formed in the front support  18  and are located radially inside the twin clutch assembly  32 , thereby minimizing the axial length of the assembly. Hydraulic passage  38  is aligned with passage  33  in the clutch hub  76  and passage  39  in the rotor hub  28 . Passages  38 ,  33 ,  39  together provide a line through which hydraulic apply pressure is communicated to the apply side of the cylinder of disconnect clutch  34 . Hydraulic passage  40  is aligned with passage  35  in the clutch hub  76  and passage  41  in the rotor hub  28 . Passages  40 ,  35 ,  41  together provide a line through which hydraulic apply pressure is communicated to the apply side of the cylinder of the launch clutch  36 . Hydraulic passage  42  is aligned with passage  37  in the clutch hub  76  and passage  43  in the rotor hub  28 . Passages  42 ,  37 ,  43  together provide a line through which fluid is supplied to the balance volumes of disconnect clutch  34  and launch clutch  36 , respectively. 
       FIG. 1  shows a hydraulic fluid passage  45  formed in the front support  18 , through which hydraulic path  38  is pressurized and vented. Similar passages are formed in the front support  18  for pressurizing and venting hydraulic path  40  and for supplying fluid to path  42 . 
     A sensor  44 , located adjacent a sensor wheel  46  secured to the rotor hub assembly  22 , produces an electronic signal representing the rotational speed and angular position of the rotor  12 , in response to movement of the wheel. The sensor  44  and sensor wheel  46  are located radially outside and axially rearward of the twin clutch assembly  32 . 
     A seal cover assembly  48 , secured to the clutch housing  20 , hydraulically and physically separates the twin clutch assembly  32  from an integrated flywheel/damper assembly  50  and the rest of the engine compartment. The seal cover assembly  48  includes an outer, static hydraulic seal  52  and an inner, dynamic hydraulic seal  54 . The outer seal  52  prevents fluid leakage past the seal at the clutch housing  20  interface; the inner seal  54  prevents fluid leakage past that seal at the twin clutch assembly  32  interface. The inner seal  54  is a relatively small diameter radial seal, which minimizes sliding resistance produced by the seal between the seal cover  48  and the engine output. 
     The integrated flywheel/damper assembly  50  is secured at its input side by bolts  56  to the engine shaft  10  and is connected at its output side by a spline  58  to a clutch shell  60 . The flywheel/damper assembly  50  contains compression springs  62  arranged mutually in parallel in the annular damper recess  63 . The springs  62  are actuated by rotational displacement of the engine shaft  10  relative to the drive hub  64  causing the springs to compress and expand in frictional contact with walls of the damper recess  63 , thereby dampening the relative torsional displacement. In this way, the flywheel/damper assembly  50  transmits input engine torque to the twin clutch assembly  32 . The cover plate  66  of the flywheel/damper assembly  50  is secured by bolts  65  to the flywheel portion  67 , which is secured by bolts  56  to the engine shaft  10 . 
     The integrated flywheel/damper assembly  50  is located outside the space that is sealed by the seal cover assembly  48  and radial outward of the engine shaft. Its location makes efficient use of the space provided, and although the sealed volume is located close to the damper, it is hydraulically isolated from the damper. The integrated flywheel/damper assembly  50  also incorporates a viscous shear plate  68  to further improve robustness and efficiency. 
     An arrangement of the elements of an assembly according to this invention as described facilitates assembly, particularly the arrangement of the seal cover assembly  48 , which separates the wet environment of the twin clutch assembly  32  and motor  14  from the dry environment of the integrated flywheel/damper assembly  50  and engine compartment. 
     The motor  14  is substantially aligned radially with the twin clutch assembly  32 , which reduces the axial length of the drive assembly and facilitates cooling the motor. The rotor hub assembly  22  and clutch shell  60  are each formed with radially directed holes  70 ,  72  distributed around the surfaces on which they are formed. The holes  70 ,  72  provide passages through which hydraulic fluid is directed from the twin clutch assembly  32  radially outward toward the motor for carrying heat from the motor to an oil cooler, where heat in the transmission fluid is transferred to ambient air before returning to a fluid sump. 
     Rotor hub assembly  22 , which is connected at its hub  28  by a spline  74  to clutch hub  76 , completes a torque path between the rotor  12  and clutch hub  76 . Disconnect clutch  34  alternately closes and opens a drive connection between clutch hub  76  and engine shaft  10  through the flywheel damper  50 , spline  58  and clutch shell  60  as clutch  34  is engaged and disengaged, respectively. 
     Clutch shell  78  is connected by spline  80  to input shaft  16 . Launch clutch  36  alternately closes and opens a drive connection between input shaft  16  and clutch hub  76  as clutch  36  is engaged and disengaged, respectively. 
     In  FIG. 2 , an engaged state of clutches  34 ,  36  is indicated by “ 1 ” and their disengaged state by “ 0 ”. A closed drive connection between the input shaft  16  and either the motor  14  or engine shaft  10  due to the state of the clutches is represented “ 1 ” and a corresponding open drive connection by a “ 0 .” When clutches  34  and  36  are disengaged concurrently, input shaft  16  is driveably disconnected from the engine shaft  10  and rotor  12 . When clutch  36  is engaged and clutch  34  is disengaged, input shaft  16  is driveably connected to the rotor  12 , but the engine shaft  10  remains disconnected from the input shaft. When clutches  34  and  36  are engaged concurrently, input shaft  16  is driveably connected to the engine shaft  10  and rotor  12 . 
     The drive assembly is assembled in steps beginning with the front support  18  and clutch housing  20 , to which sensor  44  is attached. The rotor hub  22  is inserted into the front support  18  with the sensor wheel  46  attached. Then the clutch hub  76  and clutches  34 ,  36  are installed, and the clutches are secured to the hub by snap rings. The cylinder for clutch  36  is installed first followed by the cylinder for clutch  34 . The seal cover assembly  48  is installed over the clutches. Finally, the flywheel and damper assembly  50  is installed on the engine shaft  10  prior to connecting the engine to the transmission. 
     The assembly provides support for the motor  14  and twin clutch assembly  32 , provides hydraulic paths to the clutches  34 ,  36 , and incorporates a flywheel and damper assembly  50  in a compact, short axial length arrangement that is functionally robust and easy to assemble. 
     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.