Axially collapsible driveshaft assembly

A driveshaft assembly that is axially collapsible in a reliably controlled manner includes a male splined slip yoke that cooperates with a female splined transition member for concurrent rotational movement and for relative axial movement. The transition member is, in turn, secured to a hollow cylindrical driveshaft tube. The transition member has an inner surface that tapers or otherwise extends radially inwardly, and a wedge is supported within the transition member. When a large compressive force is applied to the ends of the driveshaft assembly, the slip yoke causes the wedge to move axially relative to the transition member, thereby causing the transition member and a portion of the hollow cylindrical driveshaft tube to be expanded radially outwardly and creating a weakened region. When the wedge is moved yet axially further relative to the transition member, the driveshaft tube is further deformed in a controlled and consistent, thereby absorbing energy from the collision. Optionally, a bladder may be provided within the hollow cylindrical driveshaft tube and filled with a material so as to allow the amount of compressive force that is required to cause the driveshaft assembly to axially collapse to be varied.

BACKGROUND OF THE INVENTION

This invention relates in general to drive train systems for transferring rotational power from a source of rotational power to a rotatably driven mechanism. In particular, this invention relates to an improved structure for a driveshaft assembly, such as for use in a vehicular drive train system, that is axially collapsible in a reliably controlled manner in the event of a collision.

Torque transmitting shafts are widely used for transferring rotational power from a source of rotational power to a rotatably driven mechanism. For example, in most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical vehicular drive train system includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of misalignment between the rotational axes of these three shafts.

A recent trend in the development of passenger, sport utility, pickup truck, and other vehicles has been to design the various components of the vehicle in such a manner as to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle. As a part of this trend, it is known to design the drive train systems of vehicles so as to be axially collapsible. To accomplish this, the driveshaft tube may be formed as an assembly of two or more components that are connected together for concurrent rotational movement during normal operation, yet which are capable of moving axially relative to one another when a relatively large axially compressive force is applied thereto, such as can occur during a collision. A variety of such axially collapsible driveshaft assemblies are known in the art. However, in known axially collapsible driveshaft assemblies, it has been found to be relatively difficult to reliably control the manner in which the axially collapsing movement of the driveshaft assembly occurs. Thus, it would be desirable to provide an improved structure for a driveshaft assembly, such as for use in a vehicular drive train system, that is axially collapsible in a reliably controlled manner in the event of a collision.

SUMMARY OF THE INVENTION

This invention relates to an improved structure for a driveshaft assembly, such as for use in a vehicular drive train system, that is axially collapsible in a reliably controlled manner in the event of a collision. The driveshaft assembly includes a male splined slip yoke that cooperates with a female splined transition member so as to be connected together for concurrent rotational movement and for relative axial movement. The transition member is, in turn, secured to a hollow cylindrical driveshaft tube. The transition member has an inner surface that tapers or otherwise extends radially inwardly, and a wedge is supported within the transition member. When a large compressive force is applied to the ends of the driveshaft assembly, such as might occur during a collision, the slip yoke is initially moved axially within the transition member until the end thereof abuts the wedge. Further axial movement of the slip yoke relative to the transition member causes the wedge to move axially also relative to the transition member, thereby causing the transition member and a portion of the hollow cylindrical driveshaft tube to be expanded radially outwardly. This radial expansion or bulge of the transition member and the hollow cylindrical driveshaft tube creates an axially weakened region therein at a predetermined location on the driveshaft assembly. Consequently, when the slip yoke and the wedge are moved yet axially further relative to the transition member, the driveshaft tube is further deformed in a controlled and consistent, thereby absorbing energy from the collision. Optionally, a bladder may be provided within the hollow cylindrical driveshaft tube and filled with a material so as to allow the amount of compressive force that is required to cause the driveshaft assembly to axially collapse in the manner described above to be varied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated inFIGS. 1 and 2an axially collapsible driveshaft assembly, indicated generally at10, in accordance with this invention. The driveshaft assembly10may, for example, be used in a drive train system of a vehicle to transmit rotational power from an engine/transmission assembly (not shown) to a plurality of driven wheels (not shown), such as in the manner described above. The illustrated driveshaft assembly10is, in large measure, conventional in the art and is intended merely to illustrate one environment in which this invention may be used. Thus, the scope of this invention is not intended to be limited for use with the specific structure for the driveshaft assembly10illustrated inFIG. 1or with vehicle drive train systems in general. On the contrary, as will become apparent below, this invention may be used in any desired environment for the purposes described below.

The illustrated driveshaft assembly10includes a slip yoke11having a hollow cylindrical sleeve portion12and a pair of opposed yoke arms13. A conventional cross assembly, indicated generally at14, is connected to the opposed yoke arms13of the slip yoke11and is adapted to form a portion of a first conventional universal joint. A plurality of outwardly extending male splines12aare formed or otherwise provided on the outer surface of the sleeve portion12of the slip yoke11. The sleeve portion12of the slip yoke11extends co-axially within a first end of a hollow cylindrical transition member15of the driveshaft assembly10. A plurality of inwardly extending female splines15aare formed or otherwise provided on the inner surface of the first end of the transition member15. The outwardly extending male splines12aprovided sleeve portion12of the slip yoke11cooperate in a conventional manner with the inwardly extending female splines15aprovided on the transition member15such that the slip yoke11and the transition member15are connected together for concurrent rotational movement, while a limited amount of axial movement is permitted to occur therebetween.

An external sealing assembly is provided to prevent dirt, water, and other contaminants from entering into the region of the cooperating splines12aand15aof the slip yoke11and the transition member15from the exterior of the driveshaft assembly10. The external sealing assembly includes a hollow cylindrical cover16having a first end that is press fit or otherwise secured to the slip yoke11and a second end that extends co-axially about the first end of the transition member15. The external sealing assembly also includes a flexible boot17having a first end that is connected to the second end of the hollow cylindrical cover16and a second end that is connected to the transition member15. In a manner that is well known in the art, the flexible boot17can axially expand and contract so as to accommodate relative axial movement between the slip yoke11and the transition member15, while maintaining a reliable seal therebetween to prevent contaminants from entering into the region of the cooperating splines12aand15aof the slip yoke11and the transition member15from the exterior of the driveshaft assembly10. If desired, a conventional weld ring18may be supported on the outer surface of the hollow cylindrical cover16to facilitate the securement of one or more balance weights (not shown) thereto to balance the driveshaft assembly10for rotation in a conventional manner.

An internal sealing assembly is also provided to prevent dirt, water, and other contaminants from entering into the region of the cooperating splines12aand15aof the slip yoke11and the transition member15from the interior of the driveshaft assembly10. The internal sealing assembly includes a hollow cylindrical sealing cup19that is press fit or otherwise secured to inner surface of the sleeve portion12of the slip yoke11. In a manner that is well known in the art, the sealing cup19prevents contaminants from passing through the sleeve portion12of the slip yoke11into the region of the cooperating splines12aand15a.

A second end of the transition member15is secured to a first end of a hollow cylindrical driveshaft tube20in a conventional manner, such as by a weld21. A second end of the driveshaft tube20is secured to a tube yoke22in a conventional manner, such as by a weld23. The tube yoke22includes a hollow cylindrical sleeve portion24that extends within the second end of the driveshaft tube20and a pair of opposed yoke arms25. A conventional cross assembly, indicated generally at26, is connected to the opposed yoke arms25of the tube yoke22and is adapted to form a portion of a second conventional universal joint.

As best shown inFIG. 3, the second end of the transition member15has an inner surface that tapers or otherwise extends radially inwardly. In the illustrated embodiment, the wall thickness of the second end of the transition member15is somewhat enlarged, thereby defining the inwardly extending inner surface. More specifically, the enlarged second end of the transition member15has an annular groove30formed or otherwise provided in the inwardly extending inner surface that defines first and second inwardly extending lip portions31and32. The first and second lip portions31and32define respective inner surfaces, and the inner surface defined by the first lip portion31is slightly larger than the inner surface defined by the second lip portion32.

A wedge, indicated generally at35, is supported within the second end of the transition member15. In the illustrated embodiment, the wedge35is a generally cup-shaped member including a generally hollow cylindrical wall portion36and a generally flat annular end wall portion37. However, the wedge35may be formed having any desired shape. The hollow cylindrical wall portion36has an outer surface36athat is tapered or otherwise extends radially outwardly. As best shown inFIG. 3, the tapered outer surface36aof the wedge35is disposed within the tapered inner surfaces31and32of the second end of the transition member15and engages the inwardly extending inner surface provided thereon. The wedge35may, if desired, be positively retained within the second end of the transition member15in any desired manner. For example, the wedge35may be installed within the second end of the transition member15in a press fit or snap fit relationship. Alternatively, a portion of the second end of the transition member15may be deformed, such as by staking, magnetic pulse forming, mechanical crimping, or roll forming, so as to positively engage a portion of the outer surface of the wedge35. Thus, the wedge35is supported within the second end of the transition member15. If desired, an O-ring38or similar sealing structure may be provided to prevent dirt, water, and other contaminants from passing between the tapered outer surface36aof the wedge35and the tapered inner surfaces31and32of the second end of the transition member15into the region of the cooperating splines12aand15aof the slip yoke11and the transition member15.

Optionally, a mechanism is provided for varying the amount of compressive force that is required to cause the driveshaft assembly10to axially collapse in the manner described above. In the illustrated embodiment, this mechanism is a bladder40that is provided within the hollow cylindrical driveshaft tube20. The bladder40is preferably formed from a relatively flexible material, such as an elastomeric material. However, the bladder40may be formed from any desired material. The bladder40may be filled, either partially or fully, with a quantity of any desired material. This material may be either a solid material (such as, for example, an open or closed cell material or a solid foam material), a liquid material (such as, for example, a liquid foam material, a gelatinous material, a silicone material, water, or grease), or a gaseous material (such as, for example, air). The bladder40may, if desired, be disposed within a chamber defined within the hollow cylindrical driveshaft tube20by a pair of plates41and42. The plates41and42can be formed from any desired material and can be supported within the hollow cylindrical driveshaft tube20in any desired manner. In the illustrated embodiment, the first plate41abuts the end of the wedge35, while the second plate42abuts the end of the sleeve portion24of the tube yoke22. The purpose for the optional bladder40and the plates41and42will be explained in detail below.

The operation of the driveshaft assembly10will now be described. As discussed above, the driveshaft assembly10may be used in a drive train system of a vehicle to transmit rotational power from an engine/transmission assembly (not shown) to a plurality of driven wheels (not shown). As also discussed above, the slip yoke11and the transition member15are connected together for concurrent rotational movement, while a limited amount of axial movement is permitted to occur therebetween. During normal operation of the driveshaft assembly10, the end of the hollow cylindrical sleeve portion12of the slip yoke11is spaced apart from the generally hollow cylindrical wall portion36of the wedge35, as shown inFIG. 3.

When a large compressive force is applied to the ends of the driveshaft assembly10, such as might occur during a collision, the slip yoke11is initially moved axially within the transition member15until the end of the sleeve portion12of the slip yoke11abuts the generally hollow cylindrical wall portion36of the wedge35, as shown inFIGS. 1 and 3. Further axial movement of the slip yoke11relative to the transition member15causes the wedge35to move axially also relative to the transition member15. As a result of the engagement between the tapered outer surface36aof the wedge35and the tapered inner surfaces31and32of the second end of the transition member15, such further axial movement of the slip yoke11and the wedge35causes the second end of the transition member15to be expanded radially outwardly, as shown generally at50inFIGS. 2 and 4.

Because it is welded to the second end of the transition member15, the first end of the hollow cylindrical driveshaft tube20is also expanded radially outwardly. This radial expansion or bulge50of the second end of the transition member15and the first end of the hollow cylindrical driveshaft tube20creates an axially weakened region therein that is located at predetermined positions on the transition member15and the driveshaft tube20. Consequently, when the slip yoke11and the wedge35are moved yet axially further relative to the transition member15, the first end of the driveshaft tube20is further deformed, as shown generally at51inFIG. 5. Because of the cooperation of the wedge35with the second end of the transition member15, such additional deformation will occur consistently at the same location within the driveshaft assembly10. Also, energy from the collision is effectively absorbed by the driveshaft assembly10by virtue of the deformation50and51.

The amount of energy that is required to cause the driveshaft assembly10to axially collapse in the manner described above is dependent upon a number of factors, including, for example, the size and type of the material that is used to form the various components thereof. The bladder40described above may be used to define an additional or predetermined amount of force that is required to initiate the axially collapsing movement of the driveshaft assembly10. As discussed above, the bladder40is preferably formed from a relatively flexible material and is filled, either partially or fully, with a quantity of a material. Thus, a certain amount of energy is required to axially collapse the bladder40and the material contained therein. As also discussed above, the bladder40is disposed within a chamber defined within the hollow cylindrical driveshaft tube20by the first plate41(which abuts the end of the wedge35) and the second plate42(which abuts the end of the sleeve portion24of the tube yoke22). Thus, the bladder40reacts between the wedge35(which, during a collision, is attempted to be moved axially relative to the transition member15) and the sleeve portion24of the tube yoke22(which essentially is immovable during the collision). By varying the amount and nature of the material that is contained within the bladder40, the amount of compressive force that is required to cause the driveshaft assembly10to axially collapse in the manner described above can be varied.