Abstract:
A launch and disconnect clutch for the electric motor of a P2 hybrid powertrain is compact and provides improved operation. The clutch is mounted between the engine and transmission in the space formerly occupied by the torque converter. The clutch assembly is configured so that actuation, compensation and cooling are provided by only two oil channels. The clutch utilizes single-sided reaction plates which achieve high clutch gain thereby providing high torque capacity under electric operation and improved launch shudder characteristics.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/432,178, filed Jan. 12, 2011, which is hereby incorporated in its entirety herein by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates to a clutch for a P2 hybrid powertrain and more particularly to a launch and disconnect clutch for a P2 hybrid power train for a motor vehicle. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0004]    Extensive engineering and design effort is currently directed to hybrid powertrains for motor vehicles, especially passenger cars. One of the most promising and active areas involves the addition of an electric motor and an associated battery and electronic controller to a motor vehicle powertrain to supplement torque for launches in order that a smaller internal combustion engine may be utilized in the vehicle. Lower horsepower and smaller displacement engines routinely provide improved fuel economy over larger engines and, when supplemented by an electric motor for vehicle launch, provide entirely satisfactory overall performance. 
         [0005]    Accordingly, many hybrid powertrains begin as adaptations of conventional and existing powertrains utilizing an internal combustion engine and a transmission having a torque converter and multiple planetary gear assemblies. Into this powertrain is added an electric motor and an appropriate launch and disconnect clutch. Frequently, the torque converter is removed. The addition is not without significant challenges, however, as such constraints as axial length, housing outside diameter, clutch actuation, clutch cooling and integration into the existing powertrain components must be addressed and resolved. 
         [0006]    The present invention is directed to a launch and disconnect clutch for a P2 hybrid powertrain which addresses and solves the above-delineated challenges. 
       SUMMARY 
       [0007]    The present invention provides a launch and disconnect clutch for the electric motor of a P2 hybrid powertrain. The clutch is mounted between the engine and transmission in the space formerly occupied by the torque converter. The clutch assembly is configured so that actuation, compensation and cooling are provided by only two oil channels. The clutch utilizes single-sided reaction plates which achieve high clutch gain thereby providing high torque capacity during electric operation and improved launch shudder characteristics. 
         [0008]    Thus it is an aspect of the present invention to provide a launch and disconnect clutch for a P2 hybrid powertrain. 
         [0009]    It is a further aspect of the present invention to provide a launch and disconnect clutch for the electric motor of a P2 hybrid powertrain. 
         [0010]    It is a still further aspect of the present invention to provide a launch and disconnect clutch for mounting between the engine and transmission of a hybrid powertrain. 
         [0011]    It is a still further aspect of the present invention to provide a launch and disconnect clutch for a P2 hybrid powertrain in the space typically occupied by the torque converter. 
         [0012]    It is a still further aspect of the present invention to provide a launch and disconnect clutch for a P2 powertrain configured so that actuation, compensation and cooling are provided by only two oil channels. 
         [0013]    It is a still further aspect of the present invention to provide a launch and disconnect clutch for a P2 powertrain utilizing single-sided reaction plates which achieve high clutch gain. 
         [0014]    It is a still further aspect of the present invention to provide a launch and disconnect clutch for a P2 powertrain utilizing single-sided reaction plates which achieve high clutch gain and torque capacity under electric operation and reduced launch shudder. 
         [0015]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0016]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0017]      FIG. 1  is a block diagram of a P2 hybrid powertrain incorporating the present invention; 
           [0018]      FIG. 2  is a fragmentary, sectional view of a portion of a P2 hybrid powertrain transmission incorporating the present invention; and 
           [0019]      FIG. 3  is an enlarged, fragmentary, sectional view of a launch/disconnect clutch and compensator according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0021]    With reference to  FIG. 1 , a P2 hybrid powertrain incorporating the present invention is generally illustrated and designated by the reference number  10 . The P2 hybrid powertrain  10  includes a prime mover  12  such as an internal combustion gas, Diesel or flex-fuel engine. The prime mover  12  directly drives a damper  14  which, in turn, directly drives an electric motor and clutch module or assembly  16 . The output of the electric motor and clutch assembly  16  directly drives a transmission  18  typically including a plurality of planetary gear sets (not illustrated) which provide drive torque to an output shaft  20 . 
         [0022]    Referring now to  FIGS. 2 and 3 , the prime mover  12  includes a crankshaft  22  which is secured to an input plate  24  of the damper  14 . An output plate  26  of the damper  14  is coupled though a splined interconnection  28  to a clutch (input) hub  30  of the electric motor and clutch assembly  16 . The clutch (input) hub  30  is supported for rotation on a first roller bearing assembly  32  which, in turn, is supported by a motor hub  34 . The motor hub  34  is supported for rotation on a first ball bearing assembly  36  which is mounted in a stationary web or flange or bulkhead  38 . A fluid tight seal  42  also extends between the input hub  30  and the web or flange  38  and separates a dry region which contains the damper  14  and a wet region which contains the components of the electric motor and clutch module or assembly  16 . 
         [0023]    The electric motor and clutch module or assembly  16  includes an electric motor  50  having a stator  52  and a rotor  54 . The stator  52  is disposed within and secured to a housing  56  and is therefore stationary. Electric power is provided to the stator  52  through electrical conductors or cables  58  which pass through the housing  56  in suitable sealing and insulating feedthroughs (not illustrated). Cooling oil is provided to the periphery of the stator  52  through an oil or hydraulic fluid line  62 . The oil line  62  opens into a circumferential or annular region  64  which surrounds the periphery of the stator  52 . A circumferential or annular plate or separator  66  defining a plurality of through openings or apertures  68  evenly distributes the cooling oil around the stator  52 . 
         [0024]    The rotor  54  of the electric motor  50  is coupled to a clutch (output) hub  70  which is also coupled to and supported by the motor hub  34 . The clutch (input) hub  30  includes male splines  72  which engage complementary female splines  74  on a first plurality of single sided friction clutch plates or discs  76 . The first plurality of single sided friction clutch plates or discs  76  are interleaved with a second plurality of single sided clutch plates or discs  78  having male splines  82  which engage complementary female splines  84  on the clutch (output) hub  70 . At the ends of the friction clutch pack comprising the first and second pluralities of clutch plates  76  and  78 , are a pair of annular end plates  86  which are retained on the clutch (output) hub  70  by a snap ring  88  or a similar device. 
         [0025]    The clutch (output) hub  70  is also supported for rotation by a second ball bearing assembly  92  and, through a splined interconnection  94 , drives an input shaft  96  which supplies drive torque to the planetary gear sets of the transmission  18 . 
         [0026]    The input shaft  96  of the transmission  18  is coupled to and drives a hydraulic pump  100  which may be a vane, gear or gerotor pump. The pressurized output of the hydraulic pump  100  is fed through an outlet line (not illustrated) to a valve body (also not illustrated) and other components of the transmission  18 . Pressurized oil or hydraulic fluid flow from the valve body returns in a line  104  and flows though an axial and oblique passageway  106  and into a compensating chamber  108  of a hydraulic clutch actuator assembly  110 . The compensating chamber  108  is defined by a balance dam or compensator  112  and a piston  116 . The balance dam or compensator  112  is circular with radially oriented inner and outer end regions connected by an axial, cylindrical region. The outer (larger diameter) edge includes a seal  118  which seals against an inner surface of the piston  116 . A compression spring  122  extends between the compensator  112  and the piston  116  and functions as a return spring for the piston  116 . The inner (smaller diameter) edge of the compensator  112  abuts a snap ring  124  which limits translation of the compensator  112 . The snap ring  124  is set into a plurality of shallow channels or female splines  126  which provide a plurality of paths for hydraulic fluid or oil low toward a plurality of radial passageways  80  which like wise provide a plurality of paths for the fluid or oil toward the friction clutch plates or discs  76  and  78  to achieve cooling thereof. Such fluid or oil exits the region of the friction clutch plates or discs  76  and  78  through a plurality of oblique passageways  128 . 
         [0027]    The input shaft  96  of the transmission  18  also includes an internal axial passageway  130  which is selectively provided with pressurized oil or hydraulic fluid from the valve body to control actuation of the piston  116  and engagement of the friction clutch plates or discs  76  and  78 . Pressurized oil or hydraulic fluid in the axial passageway  130  flows into an oblique passageway  132  and into an actuation chamber  134 . The piston  116  which is shaped somewhat similarly to the balance dam or compensator  112  includes seals  138  which contain the pressurized oil or hydraulic fluid within the actuation chamber  134 . Increased hydraulic fluid or oil pressure within the actuation chamber  134  translates the piston  116  against the compression spring  122  and toward the friction clutch plates or discs  76  and  78 , compressing them and connecting the clutch input hub  30  to the clutch output hub  70  to allow torque transfer therebetween. 
         [0028]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.