Abstract:
A torsional vibration damper includes an inertia mass and a rotating shaft or hub with an elastomeric ring between the inertia mass and the rotating shaft or hub. A large portion of said elastomeric member is located in a channel located either in the inertia mass or in the hub. This allows one to achieve high contact pressure without creating a significant fatigue on the elastomeric member. This can be used with either a crankshaft damper or an internal or external drive shaft damper.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to torsional vibration dampers and, in particular, to vibration dampers adapted to be mounted to rotatable shafts such as the crankshaft or drive shaft of an internal combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    Torsional vibration dampers are employed extensively in internal combustion engines to reduce torsional vibrations delivered to rotatable shafts. The torsional vibrations may have a considerable amplitude and, if not abated, can potentially damage gears or similar structures attached to the rotatable shaft and cause fatigue failure of the rotatable shaft. Torsional vibration dampers absorb vibration and, to a certain extent, reduce the amplitude of the vibrations by converting the vibrational energy to thermal energy as a result of the damping action. The absorption of the vibrational energy lowers the strength requirements of the rotatable shaft and, therefore, lowers the required weight of the shaft. The torsional vibration damper also has a direct effect on inhibiting vibration of nearby components of the internal combustion engine which would be affected by the vibration. 
         [0003]    Virtually all motor vehicles with internal combustion engines incorporate a “serpentine” drive belt system consisting of a single endless drive belt and a series of pulleys. The pulleys derive power from the endless drive belt and operate to drive the various vehicle accessories such as the engine fan, power steering pump, air pumps, air conditioning unit, and the alternator. The endless drive belt that drives each of these pulleys is driven by a drive pulley connected to the crankshaft of the internal combustion engine. To reduce the transfer of vibrations between the crankshaft and the serpentine drive belt system, the drive pulley may comprise a torsional vibration damper that functions to reduce the amplitude or magnitude of the angular vibrations delivered by the crankshaft. 
         [0004]    Torsional vibration dampers can also be fixed to a drive shaft. The vibration damper can be fixed either to the interior surface of a hollow drive shaft or the exterior surface of a drive shaft. 
         [0005]    The torsional vibration dampers all include an inertia mass fixed to a rotating member with a vibration absorbing material between the inertia mass and the rotating member. This elastomeric member absorbs torsional vibration. Generally, the elastomeric member is in compression between the inertia mass and the rotating member. The compression provides the requisite slip torque. Unfortunately, the compression also creates significant strain on the elastomeric member. 
         [0006]    Low strains on the elastomeric member lead to a better fatigue life, whereas high contact pressures lead to improve slip torque. Generally, dampers have been engineered to balance the strains and slip torque or contact pressure such that a relatively long fatigue life is achieved with a correspondingly acceptable slip torque. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is premised on the realization that a torsional vibration damper can be designed wherein relatively high slip torque or contact pressures can be achieved without creating high strains on the elastomeric member. The torsional vibrations of the present invention include a channel that receives a portion of the elastomeric member with a portion of the elastomeric member extending outside the channel. When the elastomeric member is partially contained in a channel and compressed, significant contact pressures can be achieved with relatively low strains and low compression. In a preferred embodiment, the elastomeric member is contained partially within a channel and compressed less than 10% to achieve the desired slip torque. 
         [0008]    The present invention can be utilized to form either a crankshaft damper or a drive shaft damper designed to be located either inside or outside of the drive shaft. 
         [0009]    The objects and advantages of the present invention will be further appreciated in light of the following detailed description and drawings in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0010]      FIG. 1  is a perspective view broken away of the present invention; 
           [0011]      FIG. 2  is a partial cross sectional view of an alternate embodiment of the present invention; 
           [0012]      FIG. 3  is a cross sectional view of a second embodiment of the present invention; and 
           [0013]      FIG. 4  is a cross sectional view broken away of a third alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    As shown in  FIG. 1 , a crankshaft torsional vibration damper  10  includes a central hub member  12  and an annular inertia mass  14  separated by an elastomeric vibration absorbing member  16 . This can be a continuous ring or an annular strip and is simply referred to as ring  16 . 
         [0015]    The central hub member  12  includes a central opening  18  which is adapted to attach to the crankshaft. Further, the hub member  12  includes a peripheral rim  19 . The rim  19  includes a channel  20  having first and second side walls  24  and  26 . 
         [0016]    In turn, the inertia mass  14  has an interior annular surface  28  and an exterior surface  30 . The exterior surface  30  in this embodiment is configured to engage a serpentine belt (not shown). However, in other embodiments a serpentine belt may not be employed. The side edges  27  and  29  of surface  28  are raised slightly about 0.5 mm, leaving a gap between the rim  19  and surface  28  of about 1.1 mm. 
         [0017]    The elastomeric ring  16  includes a portion  32  which is located in channel  20  and a portion  34  located outside of channel  20 . Preferably, the elastomeric ring  16  in a non-compressed state will fill the entire channel  20 , extending from side wall  24  to side wall  26 . Although a slight gap may be present, the gap must be totally filled when the damper is assembled. The ring can be continuous or formed from an elastomeric strip placed in channel  20 . 
         [0018]    Preferably, damper  10  is assembled by positioning the rubber ring or strip  16  within the channel  20  and forcing the mass  14  over the ring  16  forcing it into compression creating contact pressure between the mass  14  and the ring  16  and between ring  16  and the hub member  12 , holding the assembly together. 
         [0019]    Preferably, the compression required to assemble the damper should be less than 10%, preferably about 5 to 8%. This is designed to achieve a slip torque suitable for the particular application. Generally, the desired slip torque for a crankshaft damper will vary from about 600 to 2000 ft/lbs, again depending upon the desired application. 
         [0020]    In order to achieve such slip torque with such low compression, about 20% of the elastomer ring  16  must be within channel  20 . The elastomer in channel  20  is confined between walls  24  and  26 ; therefore, it cannot flow. Under compression, the elastomer in channel  20  exerts outward hydrostatic pressure increasing slip torque with minimal compression 
         [0021]      FIG. 2  shows an alternate embodiment of the crankshaft damper shown in  FIG. 1 . In this embodiment, the crankshaft damper  38  includes a hub member  40  with an annular peripheral rim  42  and an inertia mass  44  with an elastomeric member  45  between the mass  44  and the hub member  40 . The mass  44  includes an exterior surface  46 , again designed to engage a serpentine belt, and an interior surface  48  that includes a channel  50 . 
         [0022]    Elastomeric ring  45  is located in channel  50  between side walls  52  and  54  with a portion  56  of elastomeric ring  45  extending outside of channel  50 . 
         [0023]    This is assembled basically in the same manner as the crankshaft damper  10  with the elastomeric ring or strip  45  positioned within the channel  50  of the inertia mass  45 . Ring or strip  45  is compressed and mass  44  forced onto the annular peripheral rim  42  of hub  40 , providing a crankshaft damper. 
         [0024]    The present invention can also be incorporated into a drive shaft damper. As shown in  FIG. 3 , the drive shaft damper  70  includes a tubular mass  72  positioned within and affixed to the interior surface  74  of a hollow drive shaft  76  with an elastomeric ring  78  between mass  72  and interior surface  74 . 
         [0025]    Mass  72  includes an exterior circumferential channel  82 . Channel  82  includes first and second side walls  86  and  88  with a rubber member  78  positioned within the channel  82  filling the entire channel from side wall  86  to side wall  88 . A small portion  90  of the rubber member  78  extends above the exterior surface  80  of mass  72 , with a portion  92  of rubber member  78  located within the channel  82 . 
         [0026]    To form the drive shaft damper  70 , preformed elastomeric ring or strip  78  is positioned inside channel  82  and compressed and inserted into the interior of drive shaft  76 . Elastomeric ring  78  can be continuous or a strip wrapped around channel  82 . 
         [0027]    An alternate drive shaft damper  94  is shown in  FIG. 4 . The damper  94  is affixed to the exterior surface  96  of drive shaft  98 . It includes an inertia mass  100  having an internal surface  102 . The internal surface  102  includes an annular channel  104 . An elastomeric ring or strip  106  is located in channel  104  with a portion  108  of elastomeric member  106  located between the exterior surface  96  of drive shaft  98  and the mass  100 . 
         [0028]    Again, to assemble the damper  94 , the elastomeric ring or strip  106  is positioned in the annular channel  104  and compressed and forced over the exterior surface  96  of drive shaft  98 . The compressive force maintains the damper  94  in position providing the requisite slip torque. 
         [0029]    In all these embodiments, the thickness of the particular elastomeric member, as well as the relative percentage of the elastomeric member located within the channel and outside the channel is a matter of design. Preferably, only about 15-25% of the elastomeric member will be located beyond the outside of the channel. The thickness of the elastomeric member is, again, a matter of design preference. Generally, these will be from about 5 to about 10 millimeters thick. Again, this will vary based on the application. 
         [0030]    The vibration dampers of the present invention, in addition to being very versatile, provide many different advantages. With respect to the crankshaft damper in particular, the use of the channel actually provides mass savings in the hub. With all the embodiments, slip torque can be significantly increased while lowering the strain on the rubber. Also, the rubber metal interface in the channel can be left unfinished. 
         [0031]    This has been a description of the present invention along with the preferred method of practicing the present invention. However, the invention itself should only be defined by the appended claims.