Abstract:
A clutch assembly for a motor vehicle drive train is provided. The clutch assembly includes a clutch pack; a piston for engaging the clutch pack; a housing including a surface for slidably supporting the piston; a release spring for disengaging the piston from the clutch; and a bearing supporting the clutch pack. The bearing limiting axial movement of the release spring away from the piston. A method of assembling a clutch assembly is also provided.

Description:
This claims the benefit to U.S. Provisional Patent Application No. 61/898,943, filed on Nov. 1, 2013, which is hereby incorporated by reference herein. 
    
    
     The present disclosure relates generally to clutch assemblies for motor vehicle transmissions and more particularly to release springs for pistons in clutch assemblies. 
     BACKGROUND 
     U.S. Pat. No. 6,095,941 discloses a clutch assembly including a release spring retained by a snap ring. 
     SUMMARY OF THE INVENTION 
     A clutch assembly for a motor vehicle drive train is provided. The clutch assembly includes a clutch pack; a piston for engaging the clutch pack; a housing including a surface for slidably supporting the piston; a release spring for disengaging the piston from the clutch; and a bearing supporting the clutch pack. The bearing limiting axial movement of the release spring away from the piston. 
     A method of assembling a clutch assembly for a motor vehicle drive train is also provided. The method includes sliding a piston onto a surface of a housing; sliding a retainer spring against the piston; and sliding an inner race of a bearing onto the housing such that the inner race of the bearing limits axial movement of the release spring away from the piston. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described below by reference to the following drawings, in which: 
         FIG. 1  shows a clutch assembly for a transmission in a motor vehicle drive train in accordance with a first embodiment of the present invention; and 
         FIG. 2  shows a clutch assembly for a transmission in a motor vehicle drive train in accordance with a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure provides a one-way clutch inner race used as a reaction point for a clutch pack release spring. In the embodiments discussed below, the outer race serves as a clutch carrier for a series of clutch plates. The piston is released by a release spring acting between the piston and the inner race. 
       FIG. 1  shows a clutch assembly  10  for a transmission in a motor vehicle drive train in accordance with a first embodiment of the present invention. Clutch assembly  10  includes a clutch pack  11  formed by a plurality of clutch plates  12  including friction surfaces  14  on both sides thereof that are axially slidable along an outer radial surface of a bearing  18  and a plurality of clutch plates  20  that are axially slidable along an outer support  22  of a housing  24 . An axially slidable piston  26  is forced toward and away from the end clutch plate  20  to engage and disengage clutch pack  11  with an axial extension  27  thereof. In order to engage clutch pack  11 , a force exerted on piston  26  in the direction of clutch pack  11  needs to overcome a force exerted by a return spring  28  onto piston  26 . Return spring  28  is positioned radially inside of axial extension  27  and contacts piston  26  with a radially outer portion  30  thereof. An inner radial end  32  of return spring  28  is held axially in place by a snap ring  34 , which contacts return spring  28  on a side of return spring  28  opposite of a side return spring  28  that contacts piston  26 . 
     Snap ring  34  includes an inner radially extending portion  36  and an outer radially extending portion  38  that are axially offset from each other by an axially extending portion  40  connecting radially extending portions  36 ,  38 . Outer radially extending portion  38  is arranged axially further away from bearing  18  than inner radially extending portion  36  and contacts inner radial end  32  of return spring  28 . In contrast to U.S. Pat. No. 6,095,941, snap ring  34  is not machined into housing  24 . Instead, snap ring  34  is sandwich axially between a radially extending surface  68  of an axially protruding lip  44  of housing  24  and a radially extending surface  66  of inner race  56  that aligns with a radially extending surface  68 . Axially protruding lip  44  hangs over an annularly shaped blind hole  46  formed by an inner radial surface  48  of lip  44 , an axial stop  50  and a first radial support surface  52  of housing  24 . Housing  24  also includes a second radial support surface  54  radially outside of the axially protruding lip  44 , which piston  26  slides axially along during engagement and disengagement of clutch pack  11 . 
     Bearing  18  is supported by first radial support surface  52  and includes an inner race  56  contacting first radial support surface  52 , a rolling element  58  riding along inner race  56  and an outer race  60  radially outside of rolling bearing  58  that includes a splined surface for receiving clutch plates  12 . Bearing  18 , at inner race  56 , includes an axial protrusion  62  received radially inside of axially protruding lip  44  and contacting axial stop  50 . Protrusion  62  includes an outer radial surface  64  aligned with inner radial surface  48  of lip  44  that extends axially from a radial extending surface  66  of inner race  56  that aligns with a radially extending surface  68  of lip  44 . 
     To assemble clutch assembly  10 , piston  26  is first slid onto second radial support surface  54 , then retainer spring  28  is slid against piston  26 . Next, snap ring  34  is slid onto housing  24  such that inner radially extending portion  36  contacts a radially extending surface  68  of lip  44  and inner race  56 , either alone or with rolling element  58  and possibly outer race  60 , is slid onto first radial support surface  52  of housing  24  such that protrusion  62  is received radially inside of axially protruding lip  44  and contacts axial stop  50  and radially extending surface  66  of inner race  56  contacts snap ring  34  at inner radially extending portion  36  to fix return spring  28  and snap ring  34  in place. 
       FIG. 2  shows a clutch assembly  110  for a transmission in a motor vehicle drive train in accordance with a third embodiment of the present invention. Clutch assembly  110  is formed in substantially the same manner as clutch assembly  10 , with the only differences being the constructions of housing  124 , the elimination of snap ring  34  and replacing return spring  28  with a longer return spring  128 . In this embodiment, because snap ring  34  is not used for retaining return spring  128 , housing  124 , like housing  24  from the first embodiment, does not include an annular groove machined therein. Additionally, axially protruding lip  44  is replaced by a more compact axially protruding lip  124  that is spaced away from radially extending surface  66 . Instead of using the housing to help retain return spring  128 , return spring  128  is retained directly by inner race  56 . Inner race  56  is fixed in place on a first support surface  152  of housing such that inner race  56  directly contacts inner radial end  132  of return spring  128 . Radially extending surface  66  of inner race  56  forms an axial stop contacting release spring  128  to limit the axial movement of release spring  128  away from piston  26 . 
     Axially protruding lip  144  hangs over an annularly shaped blind hole  146  formed by an inner radial surface  148  of lip  144 , an axial stop  150  and first radial support surface  152  of housing  124 . Housing  124  also includes a second radial support surface  154  radially outside of the axially protruding lip  144 , which piston  26  slides axially along during engagement and disengagement of clutch pack  11 . 
     To assemble clutch assembly  110 , piston  26  is first slid onto second radial support surface  154 , then retainer spring  128  is slid against piston  26 . Next, inner race  56 , either alone or with rolling element  58  and possibly outer race  60 , is slid onto first radial support surface  152  of housing  124  such that an end of protrusion  62  is received radially inside of axially protruding lip  144  and contacts axial stop  150  and radially extending surface  66  of inner race  56  directly contacts inner radial end  132  of return spring  128  to fixed return spring  128  in place. 
     In comparison with a clutch assembly having an annular groove machined into the housing, clutch assemblies  10 ,  110  may be advantageous in that the elimination groove  42  and snap ring  34  saves cost. 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.