Abstract:
A damper is provided which includes a primary damper and a secondary damper connected for series. The damper is utilized for damping torsional vibrations in a clutch assembly and is particularly useful for connecting reciprocating piston engines with a vehicle transmission.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/570,788, filed Dec. 14, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of torsional vibration dampers in general, and more specifically to friction clutches having torsional vibration dampers. 
       BACKGROUND OF THE INVENTION 
       [0003]    Torsional vibrations are the rotational irregularities of a rotating driven component. In a vehicle drivetrain, torsional vibrations are caused by forces generated within a combustion engine by the combustion of gases during the periodic combustion process. Torsional vibrations not only emanate from the engine power pulses but also from torque spikes and from abrupt changes in driveline torque due to rapid engine acceleration and deceleration. Examples of torsional dampers for dry friction clutches can be found by a review of commonly assigned U.S. Pat. No. 8,006,820 to Bassett and U.S. patent application Ser. No. 13/398,108, filed Feb. 16, 2012 to Franke, the disclosures of which are incorporated herein. It is desirable to provide a torsional damper that is especially applicable in a heavy duty application and that is an alternative to those afore described. 
       SUMMARY OF THE INVENTION 
       [0004]    To meet the aforementioned and other desires, a revelation of the present invention is brought forth. In a preferred embodiment, the damper of the present invention includes a primary damper which is connected in series with a secondary damper. By employing a series damper arrangement, the toque will flow through the dampers in series, enabling more effective engine vibration reduction than can be achieved with parallel arranged dampers. The damping that can be achieved with the present inventive damper is comparable to damping provided by a dual mass flywheel damping system, but at a significantly lower cost. The inventive damper of the present invention can have at least two damper portions with distinct spring rates and spring travels including at least one damper portion with a softer dampening rate than the effective damping rate of either a parallel damper assembly or a single damper assembly. 
         [0005]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0007]      FIG. 1  is a perspective section view of a preferred embodiment damper according to the present invention shown in an environment of a dual plate clutch assembly; 
           [0008]      FIG. 2  is a sectional view of the damper shown in  FIG. 1 ; 
           [0009]      FIG. 3  is an enlarged sectional view of a portion of the damper shown in  FIG. 1 ; 
           [0010]      FIG. 4  is an enlarged perspective sectional view of the damper shown in  FIG. 1 ; 
           [0011]      FIG. 5  is a perspective sectional view of the damper shown in  FIG. 1 ; 
           [0012]      FIG. 6  is a section perspective view of the damper shown in  FIG. 1 ; 
           [0013]      FIG. 7  is a perspective view of a friction disc utilized in the damper shown in  FIG. 1 ; 
           [0014]      FIG. 8  is an exploded view of an alternate preferred embodiment damper of the present invention; 
           [0015]      FIG. 9A  is an exploded perspective view of various components utilized in the damper shown in  FIG. 8 ; 
           [0016]      FIG. 9B  is a perspective view of a component utilized in the damper shown in  FIG. 8 ; 
           [0017]      FIG. 10  is a partial enlarged sectional view of the damper shown in  FIG. 8 ; 
           [0018]      FIG. 11  is a view similar to that of  FIG. 10  of another alternate preferred embodiment damper according to the present invention; 
           [0019]      FIG. 12  is a perspective view of a component of the damper shown in  FIG. 11 ; 
           [0020]      FIG. 13  is a sectional view similar to that of  FIG. 2  of yet another alternate preferred embodiment damper according to the present invention; 
           [0021]      FIG. 14  is an exploded view of various components utilized in the damper shown in  FIG. 13 ; 
           [0022]      FIG. 15  is a view similar to that of  FIG. 2  of yet another alternate preferred damper according to the present invention; 
           [0023]      FIG. 16  is a perspective of a component utilized in a damper shown in  FIG. 15 ; and 
           [0024]      FIG. 17  is a section perspective view of another alternate preferred embodiment damper according to the present invention similar to the damper shown in  FIGS. 13 and 14 , but being different in that it has only one friction disc for utilization in a single plate clutch assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
         [0026]    Referring to  FIGS. 1-7 , a preferred embodiment damper  7  is provided and is shown in  FIGS. 1-3  in the environment of its accompanying dual friction plate clutch assembly  10 . The damper  7  has torsionally connected thereto a first friction disc  12  and a second friction disc  14 . The friction disc  12  is fabricated from a base plate  16  ( FIG. 6 ). On opposing sides of the base plate  16  are rivet attached reinforcement plates  18  having friction pads  20  mounted thereon. The friction disc  12  has an inner peripheral edge torsionally connected by welding or by some type of geometric interlock with an outer drum  22 . Opposite the friction disc  12  connection with the outer drum  22  the outer drum on its outer peripheral surface has a series of spline teeth  24  ( FIG. 5 ). The spline teeth  24  allow the second friction disc  14  to be torsionally connected thereto and to also allow the second friction disc  14  to have relative axial movement with respect to the first friction disc  12  by virtue of its spline inner peripheral edge  26 . The outer drum  22  along its inner diameter peripheral surface has a mechanically interlocking relationship with a first disc assembly  30 . First disc assembly  30  has a center disc plate  34  ( FIG. 3 ). The disc plate  34  is captured between two reinforcing plates  36 . The disc plate  34  and reinforcing plates  36  can be similar to those described in previously mentioned co-assigned U.S. Pat. No. 8,066,820. The plates  36  and disc  34  are held together by a series of geometrically spaced rivets  40  forming the first disc assembly of the damper. 
         [0027]    The first disc assembly  30  has a series of apertures  42 . Positioned within this series of geometrically spaced apertures  42  are a first plurality of coil damping springs  44 . The disc assembly  30  provides a drive element into the springs  44  in a manner similar to that described in aforementioned in U.S. Pat. No. 8,066,820. 
         [0028]    Axially capturing first disc assembly  30  is a first hub assembly  50 . The first hub assembly includes axially spaced apart spring cover plates  52 . The spring cover plates  52  are connected by a series of rivets  54  with a hub rim  56 . The spring cover plates  52  have a series of apertures  58  ( FIG. 4 ) allowing space for the heads of the rivets  40 . The spring cover plates  52  have a series of apertures  60  which mount the springs  44  and allow the first hub assembly  50  to be torsionally associated and driven through the springs  44  by the first disc assembly  30 . The combination of the first disc assembly and the first hub assembly provide a primary damper. 
         [0029]    Torsionally connected to the primary damper inboard spring cover plate  52  typically by a mechanical interlock is a connector ring or inner drum  62 . The inner drum  62  on an end opposite the primary damper inboard spring cover plate is torsionally connected typically by a mechanical interlock with a second disc assembly  64  ( FIG. 5 ). The second disc assembly  64  includes a disc plate  66  connected with lateral reinforcing plates  67  ( FIG. 3 ) via rivets  68  ( FIG. 6 ). The second disc assembly  64  is substantially similar to the first disc assembly  30  with the exception that it is torsionally connected with the inner drum  62  rather than with the outer drum  22 . The aperture  70  of the second disc assembly  64  mounts a second plurality of springs  72 . The second plurality of springs typically has a spring constant that is a greater, equal or lesser than the spring constants of the springs  44 . The spring constant will be varied based on the driveline and damping requirements of a particular truck or user. 
         [0030]    Capturing the springs  72  are two spring cover plates  74 . The spring cover plates  74  are attached by a series of rivets  76  with a hub  78  to provide a second hub assembly  79 . The hub  78  along its inner diameter has a series of spline teeth  80  torsionally connected with a transmission input shaft  82 . 
         [0031]    In operation, a flywheel  83  is torsionally connected with an crankshaft of an engine (not shown). The flywheel  83  is also torsionally connected with a clutch assembly cover  86 . An intermediate plate  84  is torsionally connected by lugs (not shown) with the clutch assembly cover  86 . The clutch cover  86  mounts a series of coil springs  88  which bias a spring retainer  90  to urge a lever  92  to push a pressure plate  94  towards friction disc  12  and  14  which are captured respectively between the pressure plate  94  and the intermediate plate  84  and the intermediate plate  84  and the flywheel  83 . Therefore, torque is transferred from the flywheel  83  to the friction discs  12  and  14 . Torque from the friction discs  12  and  14  is then thereafter transferred to the outer drum  22  and then to the first disc assembly  30 . Torque from the first disc assembly  30  is transferred to the plurality of springs  44  and then into the first hub assembly  50 . Torque is transferred from the first hub assembly  50  to the second disc assembly  64  via the inner drum  62 . From the second disc assembly  64 , torque is transferred through the second plurality of damping coil springs  72  into the second hub assembly  89  and thereafter through hub  78  through splined teeth  80  into the transmission shaft  2 . An optional lower spring constant of the first plurality of damping springs  42  provides a “softer” damping which is typically advantageous of engines having their peak torque at lower revolution per minute (RPM) values. 
         [0032]    Referring to  FIGS. 8-10 , an alternate preferred embodiment damper  207  according to the present invention is provided. The damper  207  is similar to damper  7  as previously described with certain modifications. A first friction disc  212  has a metallic plate  218  with an “L” shape bend. This “L” shaped bend forms a tubular section  217  with rectangular cutouts  215 . A single piece first plate assembly  222  is provided. The first plate assembly  222  in combination with the tubular portion  217  of the friction plate assembly interlock by having a tab  213  of the first disc assembly  222  interlocked within the cutouts  215  of the first friction plate. In other embodiments (not shown), other means of mechanical, weld or other means of connection may be utilized. The first disc assembly  222  has a “T” shaped cross-section with a portion  223  which in combination with the tubular portion  217  of the first friction plate form a part equivalent to the previously described outer drum  22  of damper  7 . A connector ring or drum  262  torsionally connects the inboard spring plate cover  252  with the second disc assembly  270 . The inner drum  262  has a series of radially inward projecting dove tail projectors  263  to interlock within dove tail slots  253  of the inner spring cover plate  252 . The inner drum  262  has a series of axially extending rectangular tab  265  for projection within dove tail slots  279  of the second disc assembly  270 . In other embodiments (not shown), other means of mechanical, weld or other means of connection may be utilized. With this configuration, the torsional connection of the first hub assembly to the second disc assembly are both radially outward of the first and second plurality of damping springs  44  and  72 . 
         [0033]    Referring to  FIGS. 11 and 12 , an alternate preferred embodiment damper  307  according to the present invention is substantially similar to that afore described damper  207  wherein the inner torsional connective drum  362  (single stack drum) is provided and is integral with the second disc assembly  370 . The torsional connection between the second disc assembly  370  with the inboard spring cover plate  252  is slightly different in that the second disc assembly has axially extending tabs  363  for connection with the tabs  253  of the afore described spring cover plate  252 . The torsional interface between the drum portion  362  and the inboard spring cover plate  252  provides a radial interface versus the axially extending interface between the drum  262  and the inboard spring plate of the damper  207 . In other embodiments (not shown), other means of mechanical, weld or other means of connection may be utilized. 
         [0034]    Referring to  FIGS. 13 and 14 , an alternate preferred embodiment damper  407  is provided which functions essentially identically as the previously described dampers. Damper  407  differs from prior described damper in that it has a connector plate  462  which has a series of rivets  441  connecting it with the first hub assembly  250  and makes its connection with the first hub assembly at a location radially inward from the first and second pluralities of damping springs  44  and  72 . In other embodiments (not shown), other means of mechanical, weld or other means of connection may be utilized. The connector plate  462  has a series of axially extending tabs  463  which extends into dove tail slots  279  as previously described for the second disc assembly  277  of the secondary damper. In other embodiments (not shown), other means of mechanical, weld or other means of connection may be utilized. The torsional connection with the secondary damper is radially outward of the first damping springs  44  and second damping springs  72 . Therefore, torsional transfer from the hub extends through the connecting plate and does not extend through the inboard spring cover plate as do the previously described embodiments. This lessens the chance of distortion of the spring cover plate and also provides the advantage of higher torque capacity by fully utilizing the primary function of the spring covers to share the torque and transfer that to the connecting plate which can transfer a higher range of torque without damaging the spring cover. 
         [0035]    Referring to  FIGS. 15 and 16 , an alternate preferred embodiment damper  507  of the present invention is provided. The damper  507  is similar to those previously described with the main exception in that the connective member  562  is torsionally connected to the first hub assembly  550  via mechanical interlock or a tooth interface. The connection to the first hub assembly is radially inward the first plurality of springs  44 . The connective member  562  by a series of studs  567  is connected with the second disc assembly  570  radially inward of the second plurality of damping springs  72 . 
         [0036]    Referring to  FIG. 17 , an alternate preferred damper according to the present invention  607  is provided. Damper  607  is substantially similar to damper  407  previously described with the exception that there is only one friction disc  612 . This is for clutch assemblies without an intermediate plate. The friction disc extends over an area which is axially most closely adjacent the secondary damper  670 . 
         [0037]    The description of the invention is merely exemplary in nature and, thus, 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.