Abstract:
A decoupler assembly for a motor vehicle driveline comprising a decoupler, an input driveably connected to a transmission output shaft and including a first connection that secures the input to the decoupler, and an output driveably connected to a final drive axle then to wheels of the vehicle, including a second connection that secures the output to the decoupler, and a support that provides bending continuity between the input and the output, the support permitting rotation of the input about an axis relative to the output, the decoupler, the first connection and the second connection providing resistance to such rotation.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to a motor vehicle powertrain, and, in particular, to an apparatus for torsionally decoupling components of a vehicle powertrain. 
         [0003]    2. Description of the Prior Art 
         [0004]    Power plants used in cars, SUVs, and trucks tend to generate torsional disturbances primarily of an impulsive nature, that degrade customer-perceived noise, vibration and harshness (NVH) quality both transients including clunk, thump, rattle, roughness, and steady state disturbances including gear whine, moan, growl. The durability of vehicle powertrains, whose sources for such disturbances are an engine and transmission, can be adversely affected by these disturbances. 
         [0005]    Furthermore, a vehicle driveline, including its driveshaft and axle, has inherent torsional resonance modes that tend to be sympathetic to such disturbances or aligned with corresponding torsional modes within the transmission mechanism. This modal alignment causes significant amplification of both axle and transmission gear noise. 
         [0006]    Several types of dampers are widely used in the industry to minimize the negative effects of such tensional excitation forces. Their performance is limited to a narrow tuning frequency range and amplitude reduction provided by the mass and damping. Moreover, their complexity, added weight and cost are undesired. 
         [0007]    Other solutions use flexible couplings in lieu of typical U-joints or CV joints. However, these couplings tend to deteriorate significantly powertrain bending characteristics and significantly limit the driveline angle capacity required for a solid beam axle application, thus inducing risks to NVH quality and durability including critical speed. 
       SUMMARY OF THE INVENTION 
       [0008]    A decoupler assembly for a motor vehicle driveline comprising a decoupler, an input driveably connected to a transmission output shaft and including a first connection that secures the input to the decoupler, and an output driveably connected to wheels of the vehicle, including a second connection that secures the output to the decoupler, and a support that provides bending continuity between the input and the output, the support permitting rotation of the input about an axis relative to the output, the decoupler, the first connection and the second connection providing resistance to such rotation. 
         [0009]    The torsional decoupler reduces or eliminates the NVH issues efficiently from both transient events and steady state events. The device torsionally decouples the driveline from the power plant while maintaining the integrity of the powertrain bending characteristics and the angular capacity of the drive shaft. 
         [0010]    The flexible decoupler provides an efficient, robust solution to torque induced disturbances with a low weight penalty, precise targeting of the torsional vibration characteristics to be eliminated, while leaving all other needed design characteristics unaffected. 
         [0011]    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 
         [0012]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0013]      FIG. 1  is a schematic side view of a motor vehicle powertrain that includes a torsional decoupler assembly; 
           [0014]      FIG. 2  is cross sectional side view of a first embodiment of a decoupler assembly for use in the powertrain shown in  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view of the decoupler assembly shown in  FIG. 2 ; 
           [0016]      FIG. 4  is cross sectional side view of a second embodiment of a decoupler assembly for use in the powertrain shown in  FIG. 1 ; 
           [0017]      FIG. 5  is a perspective view of a fitting for the decoupler assembly shown in  FIG. 4 ; 
           [0018]      FIG. 6  is a perspective view of a second fitting for the decoupler assembly shown in  FIG. 4 ; and 
           [0019]      FIG. 7  is a perspective view of a second embodiment fitting for the decoupler assembly shown in  FIG. 4 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The powertrain  10  of  FIG. 1  includes an engine  12 , transmission  14  driveably connected to the engine, transmission output shaft  16  and output flange  18 , a decoupler  20 , a first universal joint  22  having a flange  24 , driveshaft  26 , second universal joint  28  having a flange  30 , and a inter-wheel differential  32 , that transmits power differentially to axle shafts  34 , which extend laterally to the wheels of the vehicle. 
         [0021]    Output shaft  16  and output flange  18  are formed as an integral unit or are connected mutually such that they function structurally as a unit. Flange  24  is secured to universal joint  22  such that they function structurally as a unit. 
         [0022]    Decoupler  20  provides bending continuity with unaffected overall rigidity, axial force continuity, and lateral force continuity between transmission output  16  and universal joint  22 , but not torsional continuity. Axial force continuity provided by decoupler  20  between transmission output  16  and universal joint  22  is represented by vectors  36 ,  37 . Lateral force continuity provided by decoupler  20  between transmission output  16  and universal joint  22  is represented by vectors  38 ,  39 . Bending continuity provided by decoupler  20  between transmission output  16  and universal joint  22  is represented by vectors  40 ,  41 , respectively. But torsional disturbance represented by vector  42  cannot be transmitted across decoupler  20  in either direction. But the nominal powertrain torque (DC torque) from output shaft  16  is entirely transmitted across decoupler  20  to the driveshaft joint  22 . 
         [0023]    A decoupler assembly  50  having the desired structural functions described with reference to  FIG. 1  is illustrated in  FIGS. 2 and 3 . Transmission output shaft  16  is an input to the decoupler assembly  50 . Flange  18  is formed with a series of tapped holes  52 , spaced angularly about an axis  54  and aligned with holes  56  formed in a flange extension  58 . A bolt  60  is fitted into each of holes  56 , and the threads of bolts  60  engage the threads tapped in holes  52 , thereby providing no bending, lateral force or axially force continuity between flange extension  58  and the transmission output shaft  16  and its flange  18 . 
         [0024]    A flexible disc decoupler  62  is not secured to output shaft  16 . The flexible decoupler  62 , which is preferably formed of flexible rubber or a flexible synthetic material, is formed with a series of holes  64 , spaced angularly about axis  54  and aligned with holes  66  formed in flange extension  58 . Cylindrical spacers  68 , located in holes  62 , each abut the axial face  70  of flange extension  58 . An attachment bolt  72 , fitted into each of holes  66  and each of sleeves  68 , is engaged by a nut  74 , thereby providing virtually no bending, lateral force or axially force continuity between flexible decoupler  62  and flange extension  58 . 
         [0025]    Decoupler  62  is also formed with a series of holes  76 , spaced angularly about axis  54  and aligned with holes  78  formed in a positioning adapter  80 . Cylindrical spacers  82 , located in holes  76 , each abut the axial face  84  of positioning adapter  80 . An attachment bolt  86 , fitted into each of holes  78  and each of sleeves  82 , is engaged by a nut  88 . 
         [0026]    Flange extension  58  is supported on a cylindrical journal  90  of positioning adapter  80  by a bearing  92  such that flange extension is free to rotate about axis  54 , but for the minimal torsional resistance provided by flexible decoupler  62 , the connection provided by bolts  72  between flange extension  80  and decoupler  62 , and the connection provided by bolts  86  between decoupler  62  and positioning adapter  80 . 
         [0027]    The universal joint  22  at the forward end of driveshaft  26  is secured to a fitting  94 , which is formed with holes  96  that are aligned with tapped holes  98  formed in positioning adapter  80 . Joint yoke with flange  94  is connected to positioning adapter  80  by bolts  100 , which are fitted into holes  96  and engaged with the threads of tapped holes  98 . 
         [0028]    In operation, bending about any axis normal to axis  54  is transmitted between output shaft  16  and fitting  94  through the torsional decoupler  50  and is carried by adapter  58 , bearing  92  and adapter  90 . A flexible, low torsional stiffness load path between output shaft  16  and fitting  94  is provided by flexible decoupler  62 , the connection provided by bolts  72  between flange extension  80  and decoupler  62 , and the connection provided by bolts  86  between decoupler  62  and positioning adapter  80 . 
         [0029]    Decoupler  110 , a second embodiment having the desired structural functions described with reference to  FIG. 1 , is illustrated in  FIGS. 4-6 . Fitting  112  includes a flange  114  formed with series of bolt holes  116 , angularly spaced about axis  54  and by which output shaft  16  is secured to fitting  112 . Fitting  112  includes three bosses  118  angularly spaced about axis  54  and formed with holes  120 . A shoulder  122  provides a surface facing a decoupler disc  124 , which is preferably formed of flexible rubber or a flexible synthetic material and with a series of holes  126 , spaced angularly about axis  54  and aligned with holes  120 . Bolts  128 , fitted in holes  126 , engage threads tapped in holes  120  and secure decoupler disc  124  and fitting  112  mutually. Fitting  112  includes a cylindrical journal  130  concentric with axis  54 . 
         [0030]    A second fitting  132  includes a flange  134  formed with series of bolt holes  136  angularly spaced about axis  54 , by which fitting  94  or universal joint  22  are secured to fitting  132 . Fitting  132  includes three bosses  138  angularly spaced about axis  54  and formed with holes  140 . A shoulder  142  provides a surface facing decoupler disc  120 , which is preferably formed with a series of holes  144 , spaced angularly about axis  54  and aligned with holes  140 . Bolts  146 , fitted in holes  144 , engage threads tapped in holes  140  and secure decoupler disc  124  and fitting  132  mutually. 
         [0031]    Fitting  132  includes a cylindrical journal  148  concentric with axis  54  and surrounding journal  130 . Roller bearings or needle bearings are located in an annular space between journals  130  and  148 . 
         [0032]    In operation, bending about any axis normal to axis  54  is transmitted between output shaft  16  and fitting  94  or universal joint  22  through the torsional decoupler  132 . The load path for transmitting bending and lateral force is provided by the overlapping journals  130 ,  148 . A highly flexible, low torsional stiffness load path between output shaft  16  and fitting  94  is provided by flexible decoupler  124 , the connection provided by bolts  128  between fitting  112  and decoupler  124 , and the connection provided by bolts  146  between decoupler  124  and fitting  132 . 
         [0033]    Each decoupler assembly  50 ,  110  may be installed at any interface in the vehicle driveline, but is preferably located at the transmission-to-driveshaft interface. Each decoupler  50 ,  110  maintains low vibration amplitudes caused by powertrain bending excitation moments by providing bending stiffness continuity. The decoupler assemblies  50 ,  110  bypass the torsional excitation disturbing moments through an independent elastic torsional spring having a low torsional stiffness. The decoupler assemblies  50 ,  110  decouple the driveline/driveshaft torsional modes of vibration from the engine/transmission torsional modes of vibration, preserve the universal joint that will the provide necessary angle capacity and shield the torsional decoupler from bending excessively, and dampen the torsional vibration amplitude for both transient events of steady state harmonics. 
         [0034]    The decoupler assemblies  50 ,  110  may include flexible decouplers  62 ,  124  that are flexible rubber circular couplings as shown in the figure, or rubber pucks arranged in a circular fashion working in compression, or metallic springs arranged in circular fashion. 
         [0035]    Preferably input shaft  16 , flange  18 , flange extension  58 , positioning adapter  80 , fitting  94 , and fittings  114 ,  134  are formed of metal having a modulus of elasticity in the range 15.0×10 6 -30.0×10 6  pounds per square inch. 
         [0036]    The flexible decoupler  62  is sized to accommodate the driveshaft-to-transmission interface standard circular flange outer diameter for the given application. The inner diameter is sized to accommodate the adapter pilot with standard bearings. The rubber durometer can range from 50 to 65 with a thickness range of 15-30 mm. An acceptable range for its torsional stiffness is 100-4500 lb-in per degree, when assembled as shown in  FIGS. 2 and 4  depending on the nominal transmitted powertrain torque and on the frequency range of the torque disturbances. 
         [0037]    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.