Patent Publication Number: US-2005137020-A1

Title: Controlled collapsible drive line arrangement

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to drive shafts for a motor vehicle, and, more particularly, to an improved collapsible drive shaft arrangement for a motor vehicle powertrain.  
     BACKGROUND OF THE INVENTION  
      Generally, drive lines in vehicle powertrains are used to connect a transmission output to a torque distribution mechanism for transmitting torque to drive wheels of a motor vehicle. The drive lines are typically rigid with universal joint (U-joint) connections as is known in the art. It is also known where a drive line has been configured in a collapsible arrangement with the drive line including two collapsible shafts that are free to slide axially relative to each other.  
      While such systems provide advantages because they are collapsible, the drive shafts of these known arrangements rely on drive line connective restraints, such as static elements, to maintain position relative to each other.  
     SUMMARY OF THE INVENTION  
      Accordingly, an improved collapsible drive shaft arrangement is provided which is able to maintain within a desired force range, the connectivity of drive line drive shaft components irrespective of other drive line powertrain components.  
      In accordance with one aspect of the present invention, a drive line is provided that includes an axially translatable coupling mechanism and first and second drive shafts. The first drive shaft is coupled to transmission and the second drive shaft is coupled to a torque distribution mechanism for distributing torque to vehicle drive wheels. The axially translatable coupling mechanism slideably couples the first and second drive shafts in an axial direction while also providing a non-rotateable connection between the drive shafts. A pin member is positioned in the axially translatable coupling mechanism and includes a predetermined shear threshold that is arranged to control the force range for which the coupling mechanism allows the drive shafts to collapse axially with respect to each other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims, and in the accompanying drawings in which:  
       FIG. 1  illustrates a side view of a drive line assembly including a controlled collapsible drive line arrangement in accordance with the present invention;  
       FIG. 2  illustrates an expanded view of a controlled collapsible coupling mechanism illustrated in  FIG. 1  in accordance with the present invention; and  
       FIG. 3  illustrates an expanded view of components of the controlled collapsible drive line assembly in a pre-assembled state in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMIENT  
      Referring now to the drawings,  FIGS. 1 and 2  illustrate an exemplary embodiment of a drive line assembly  10  with a controlled collapsible drive line arrangement in accordance with the present invention. The drive line assembly includes a first shaft section  20  and a second shaft section  30 . The first shaft  20  section is connected to a transmission at one end through a flexible coupling  40  and is also connected at another end to the second shaft section  30  by a U-joint  50 . The second shaft section  30  is connected to a differential through flexible coupling  45 . The drive line assembly  10  further includes a support  60  which is attached to a vehicle structural member (not shown).  
      The first shaft section  20  further includes a first shaft member  70  and a second shaft member  80 . The first and second shaft members are coupled together though an axially translatable coupling mechanism  90 . As best seen in  FIG. 3 , the coupling mechanism  90  includes internal splines  100  extending radially inwardly towards the center of the coupling mechanism  90 . The splines  100  mesh with external splines  110  that extend radially outwardly from first shaft member  70 .  
      The coupling mechanism  90  further includes a bore  120  that coincides with a mating bore  130  in the splined portion of the first shaft section  70  upon assembly as shown in  FIG. 3 . A shear pin member  140  is inserted into coinciding bores  120  and  130  in the assembled shaft members  70  and  80  as shown in  FIGS. 2 and 3 . In the preferred embodiment, shear pin member  140  is assembled into coinciding bores  120  and  130  in a press fit or rivet configuration.  
      In operation, the controlled collapsible shaft arrangement provides for a drive line assembly that includes a coupling arrangement which allows for controlled collapsibility in the axial direction among respective drive shaft members while maintaining a non-rotateable connection among the same respective drive shaft members. More specifically, the splines of drive shaft members  70  and  80  allow for a non-rotateable connection among shaft members  70  and  80  while also providing for an axially translatable coupling arrangement. The shear pin or rivet inserted into coinciding bores of shaft members  70  and  80  further provides for controlled axial translation or collapsibility among shaft members  70  and  80 . It should be appreciated that the shear pin can be constructed so as to have a predetermined shear threshold thus maintaining axial connectivity of shaft members  70  and  80  below a predetermined axial force while also allowing axial collapsibility if the drive line assembly experiences a force that exceeds the predetermined shear threshold of the shear pin.  
      Thus, the drive line system with a collapsible arrangement allows for axial movement among drive shaft members during normal operation. To address potential noise, vibration, and harshness (NVH) issues that may result from the relative movement during normal operation, using the shear pin or rivet arrangement in accordance with the teachings of the present invention, eliminates or significantly modifies relative movement among the coupled drive shaft members until a predetermined axial force is experienced.  
      The foregoing description constitutes the embodiments devised by the inventors for practicing the invention. It is apparent, however, that the invention is susceptible to modification, variation, and change that will become obvious to those skilled in the art. In as much as the foregoing description is intended to enable one skilled in the pertinent art to practice the invention, it should not be construed to be limited thereby but should be construed to include such aforementioned obvious variations and be limited only by the proper scope or fair meaning of the accompanying claims.