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 col- lapsible arrangement with the drive line including two col- lapsible 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 ele- ments, to maintain position relative to each other.

SUMMARY OF THE INVENTION Accordingly, an improved collapsible drive shaft ar- rangement is provided which is able to maintain within a de- sired force range, the connectivity of drive line drive shaft components irrespective of other drive line powertrain compo- nents.

In accordance with one aspect of the present invention, a drive line is provided that includes an axially translat- able coupling mechanism and first and second drive shafts.

The first drive shaft is coupled to transmission and the sec- ond 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 pro- viding a non-rotateable connection between the drive shafts.

A pin member is positioned in the axially translatable cou- pling 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 axi- ally 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 ap- pended claims, and in the accompanying drawings in which: Figure 1 illustrates a side view of a drive line assem- bly including a controlled collapsible drive line arrangement in accordance with the present invention; Figure 2 illustrates an expanded view of a controlled collapsible coupling mechanism illustrated in Figure 1 in ac- cordance with the present invention; and Figure 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, Figures 1 and 2 illus- trate an exemplary embodiment of a drive line assembly 10 with a controlled collapsible drive line arrangement in ac- cordance 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 con- nected at another end to the second shaft section 30 by a U- joint 50. The second shaft section 30 is connected to a dif- ferential through flexible coupling 45. The drive line assem- bly 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 Figure 3, the coupling mechanism 90 includes internal splines 100 ex- tending 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- ure 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 Figures 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 arrange- ment provides for a drive line assembly that includes a cou- pling 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 arrange- ment. 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 ax- ial 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 arrange- ment allows for axial movement among drive shaft members dur- ing 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 rela- tive 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 modi- fication, variation, and change that will become obvious to those skilled in the art. Inasmuch as the foregoing descrip- tion 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.