Abstract:
A torque converter includes a turbine, a lockup clutch including a piston, and a damper having at least one cover plate, the cover plate being attached directly to piston. A method for assembling the torque converter includes passing a section of the piston through a hole in the cover plate and attaching the piston to the cover plate at the hole.

Description:
Priority to U.S. Provisional Patent Application Ser. No. 60/959,262, filed Jul. 12, 2007, is claimed, the entire disclosure of which is hereby incorporated by reference herein. 
    
    
     The present invention relates generally to hydraulic torque converters, and more particularly to hydraulic torque converters having lockup clutches. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. Nos. 4,693,348, 6,325,191, and 6,615,962, hereby incorporated by reference herein, describe hydraulic torque converters with lockup clutches. 
       FIG. 1  shows an example prior art hydraulic torque converter  10  including a housing  12  non-rotatably connected to a crankshaft  14  to receive torque from an engine. Housing  12  has coaxial shells  16  and  18  secured and sealed together, for example welded. Attached to housing  12  is a pump  20  coaxial with and sharing the angular velocity of housing  12 . 
     Enclosed in housing  12  are a turbine  22  rotatable with respect to housing  12  and a stator  24  installed between pump  20  and turbine  22 . Turbine  22  is non-rotatably connected to a turbine hub  26 , and turbine hub  26  is non-rotatably connected to input shaft  28  of a transmission, by splines  30 . Stator  24  is mounted on a one-way clutch  32  connected by splines  34  to a hollow, non-rotating stator shaft  36 . 
     Prior art torque converter  10  may further include a lockup clutch  38  capable of being engaged to transmit torque directly between housing  12  and turbine hub  26 . This is accomplished by positioning a friction surface  40  of a piston  42  in contact with a friction surface  44  of housing  12 . Piston  42  is moveable in both the circumferential and axial directions around turbine hub  26 . Axial movement of piston  42  relative to turbine hub  26  may be accomplished by introducing a pressure difference between hydraulic fluid regions  45  and  46  on either axial side of piston  42 . 
     Lockup clutch  38  may also have a torsional vibration damper  48  including a drive plate  50 , cover plates  52 ,  54 , a group of coil springs or other elastic energy storing devices  56 , and rivets or spacer bolts  58 . Drive plate  50  may be connected to piston  42  with splines or crenellations  60 . Cover plates  52 ,  54  retain springs  56  and are held together with rivets or spacer bolts  58 . Cover plates  52 ,  54  may be rigidly connected to turbine  22  and turbine hub  26 . Relative circumferential motion between cover plates  52 ,  54  and drive plate  50  compresses or decompresses springs  56 . Torsional damper  48  thereby isolates turbine hub  26  from torsional vibrations coming from, for example, crankshaft  14  or engine. 
     SUMMARY OF THE INVENTION 
     The present invention provides a torque converter comprising a turbine, a lockup clutch including a piston; and a damper having at least one cover plate, the cover plate being attached directly to piston. 
     The present invention also provides a method for assembling the torque converter comprising the steps of passing a section of the piston through a hole in the cover plate, and attaching the piston to the cover plate at the hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a prior art hydraulic torque converter. 
       The present invention will be described further with respect to one embodiment using the figures, in which: 
         FIG. 2  is a sectional view of one embodiment of the present invention. 
         FIG. 3  is an exploded view of one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  shows a section of a torque converter  110  embodying the present invention. Torque converter  110  includes a housing shell  116  connected to a crankshaft of an engine. Inside housing shell  116  is a turbine  122  rigidly connected to a turbine hub  126 . Turbine hub  126  is non-rotatably connected to an input shaft  128  of a transmission, for example, by splines  130 . The engine may thus cause input shaft  128  to rotate about center axis CA. 
     Torque converter  110  further includes a lockup clutch  138  capable of being engaged to transmit torque directly between housing shell  116  and turbine hub  126 . This engagement is accomplished by positioning a friction surface  140  of a piston  142  in contact with a friction surface  144  of housing shell  116 . Piston  142  is moveable in both circumferential and axial directions around turbine hub  126 . Axial movement of piston  142  relative to turbine hub  126  may be accomplished by introducing a pressure difference between hydraulic fluid regions  145  and  146  on either axial side of piston  142 . 
     Lockup clutch  138  has a torsional vibration damper  148  for isolating turbine hub  126  from torsional vibrations caused by, for example, the crankshaft or engine. Damper  148  includes an array of coil springs or other elastic energy storing devices  156  and cover plates  152 ,  154  retaining the elastic energy storing devices  156 . Cover plates  152 ,  154  are connected to piston  142  with rivets  170  extruded from outer circumferential surface  172  of piston  142 . A flange  174  is non-rotatably connected to turbine hub  126  with, for example, splines  176 . Relative motion between cover plates  152 ,  154  and flange  174  causes springs  156  to compress or decompress. 
       FIG. 3  shows schematically a section of outer portion of piston  142  (shown schematically as curved to indicate that it is annular) and cover plates  152 ,  154  prior to assembly. Outer surface  172  of piston  142  is stamped with a crenellated geometry having alternating shoulders  178  and  180 , extending axial distances X 1  and X 2 , respectively, from entirety of piston  142 , where X 1  is greater than X 2 . Extruded further in the axial direction are rivets  170  and  171 , for example square in cross-section, attached to shoulders  178  and  180 , respectively. Rivets  170  and  171  extend axial distances X 3  and X 4 , respectively, from entirety of piston  142 , where X 3  is greater than X 4 . Distance X 1  can lie between X 2  and X 4 . Cover plates  152 ,  154  include cutouts  185 ,  187  to retain springs  156 . 
     Cover plates  152 ,  154  contain holes  182 ,  186  and slots  184  to accommodate crenellated geometry and rivets  170 ,  171  of piston  142 . Inner cover plate  152  contains holes  182  similar in cross-section to rivets  171 , and slots  184  similar in cross section to shoulders  178 . Inner cover plate  152  is assembled onto piston  142  so that rivets  171  on shoulders  180  pass through holes  182 , and shoulders  178  pass through slots  184 . Outer cover plate  154  contains holes  186  similar in cross-section to rivets  170 . Outer cover plate  154  is assembled onto piston  142  so that rivets  170  on shoulders  178  pass through holes  186 . Once cover plate  152  is properly seated onto piston  142 , rivet  171  is coined to secure cover plate  152  in position. Next, cover plate  154  is seated onto piston  142 , and rivet  170  is coined to secure cover plate  154  in position. Rivet  171  being coined before cover plate  154  is seated. 
     Attaching cover plates  152 ,  154  directly to piston  142  advantageously saves space for balancing turbine assembly  188 , shown in  FIG. 2 . Turbine assembly  188  is typically balanced with a weight attached to the outer surface  190  of turbine shell  192 . Because this weight typically is assembled perpendicular to turbine shell  192 , prior art dampers, for example  48 , can interfere with the desired placement of the weight. By attaching cover plates  152 ,  154  directly to piston  142  with rivets  170 ,  171 , the interference issue between damper  48  and balancing weight advantageously can be avoided. 
     Attaching cover plates  152 ,  154  directly to piston  142  also advantageously avoids the use of separate rivets or spacerbolts, for example  58 , to hold cover plates  152 ,  154  together. In some instances, there is not enough radial room for a rivet or spacerbolt to be positioned in a desirable location, often radially outward from springs  56 . By fixing cover plates  152 ,  154  directly to piston  142 , separate rivets or spacerbolts are advantageously not needed, saving additional space.