Background of Invention Two piece drive shaft assemblies commonly include longitudinally coupled inner and outer splined tubes for transferring torque such as used in power transmission drive shafts of motor vehicles. Examples of two piece drive shafts are shown in United States patent nos. 3,293, 884; 4,125, 000; 6,193, 612 and 6,279, 221.

The internal clearances between the coupled inner and outer splined tubes often causes wobble when the drive shaft is rotated. The wobble of the drive shaft increases the difficulty in balancing the drive shaft which results in increased vibration and reduces the efficiency in transferring torque in the power transmission.

Summary of the Invention The disadvantages of the prior art may be overcome by reducing the internal clearance between the coupled inner and outer tubes thereby reducing wobble and creating a drive shaft which is easier to balance.

According to one aspect of the invention, there is provided a drive shaft assembly comprising an inner tube having a plurality of circumferentially spaced apart outer torque driving splines and a first end formed by a swagged nose. An outer tube is also provided having a plurality of circumferentially spaced apart inner torque driving splines meshed with the outer torque driving splines. At least one projection is formed in the outer tube and spaced longitudinally from the inner torque driving splines for tight mating contact with the swagged nose of the inner tube during axial alignment of the inner tube with the outer tube.

According to another aspect of the invention there is provided a method of

forming a drive shaft assembly comprising the steps of: providing an inner tube and an outer tube; swaging a constant diameter nose on an end of the inner tube; forming at least one projection in the outer tube; and piloting the nose of the inner tube into the outer tube for mating engagement with the projection and for providing axial alignment between the inner tube and the outer tube.

Description of the Drawings In drawings which illustrate embodiments of the present invention, Figure 1 is an exploded perspective view of a two piece drive shaft assembly according to one aspect of the invention; Figure 2 is an end view of the assembled drive shaft; and Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2.

Description of the Invention Referring to Figure 1, a two piece drive shaft assembly is generally shown at 10. The drive shaft assembly 10 may be a power transmission shaft for use in a motor vehicle. The drive shaft assembly 10 includes an elongated inner tubel2 extending longitudinally between a first end 14 and a second end 16. The drive shaft assembly 10 also includes an elongated outer tube 18 extending longitudinally between a first end 20 and second end 22. The inner and outer tubes 12,18 may be steel or aluminum and may be formed in accordance with known methods.

The first end 14 of the inner tube 12 has a constant diameter swagged nose or extension 24 for telescoping or piloting receipt into the second end 22 of the outer tube 18 as will be described in greater detail below. The inner tube 12 further includes a plurality of circumferentially spaced apart, outwardly projecting, torque driving splines 26 extending longitudinally from the swagged nose 24 toward the second end 16.

The first end 20 of the outer tube 18 includes an outwardly flared yoke end 28 formed by a swaging or stamping operation. The yoke end 28 may alternatively be inwardly tapered as desired. A plurality of apertures 30 are formed in the yoke end 28

by any conventional process, such as piercing, lancing, drilling, laser cutting, etc., either before or after the swaging step. A yoke structure may be connected, preferably by welding, onto the yoke end 28 of the outer tube 18 to provide a driving connection with the drive shaft assembly 10. The second end 16 of the inner tube 12 may also include a yoke end for supporting a yoke structure similar to the outer tube 18.

The outer tube 18 also includes a plurality of circumferentially spaced apart, inwardly projecting, torque driving splines 32 longitudinally aligned with the torque driving splines 26 of the inner tube 12 for mating engagement therewith. The torque driving splines 32 extending longitudinally along the outer tube 18 and are spaced between the first end 20 and second end 22.

The outer tube 18 further includes at least one projection 33 for axially aligning and matingly engaging the swagged nose 24 upon telescoping insertion of the inner tube 12 into the outer tube 18. The projection shown in the preferred embodiment of Figure 1 includes a plurality of circumferentially spaced apart, inwardly projecting, splines 34 spaced longitudinally from, or forwardly of, the torque driving splines 32 toward the yoke end 28. The splines 34 may be of the type formed by the Grob process as described in United States Patent 3,293, 884. The splines 34 matingly engage the outer surface of the swagged nose 24 on the inner tube 12 to axially align the inner tube 12 with the outer tube 18. The splines 34 may be formed and sized to a predetermined inner root diameter when the yoke end 28 is being swagged out for the connection of the yoke structure. Alternatively, the outer tube 18 may include one or more continuous inner ribs or rings projecting inwardly, or radially, from the tube wall for mating contact with the swagged nose 24 on the inner tube 12.

Referring to Figures 2 and 3, in assembly the inner tube 12 is telescopically received in the outer tube 18. Specifically, the swagged nose 24 of the inner tube 12 is piloted into the second end 22 of the outer tube 18 and extended longitudinally until matingly engaged and surrounded by the splines 34 of the outer tube 18. The interaction between the swagged nose 24 and the splines 34 axially aligns the inner tube 12 within the outer tube 18 to prevent wobble therebetween and reduce vibration

of the drive shaft assembly 10. The torque driving splines 26 of the inner tube 12 are meshed with the torque driving splines 32 of the outer tube 18 for providing a driving connection between the inner tube 12 and outer tube 18 to transfer rotational torque along the drive shaft assembly 10.

As shown in Figure 3, the root diameter A of the swagged nose 24 is smaller than the root diameter B of the torque driving splines 26. Similarly, the root diameter C of the splines 34 is smaller than the root diameter D of the torque driving splines 32.

The clearance between the splines 34 and the swagged nose 24 is smaller or less than that between the inner and outer torque driving splines 26,32 thereby creating a tight rigid fit between the inner and outer tubes 12,18, reducing wobble in the drive shaft assembly 10, and creating a drive shaft which is easier to balance.

The above-described embodiment of the invention is intended to be an example of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention.