1. Technical Field
This invention relates to vehicle suspension systems for mounting ground-engaging wheels to a vehicle frame, and, more particularly, to a trailing arm suspension axle assembly for securing a wheel-carrying axle to a vehicle.
2. Description of Related Art
Vehicle suspensions having an arm pivotably mounted to a vehicle frame typically have an air spring mounted between a free end of the arm and the frame and an axle mounted to the top of the arm. An example of one such suspension is disclosed in the U.S. Pat. No. 3,332,701 to Masser (issued Jul. 25, 1967). In Masser '701, the axle is positioned on two bracket plates which cradle the axle. The brackets are rigidly secured to the axle by welding and are secured to the trailing arm by a bushed two-pin connection. It is also known to attach a flat plate between the bracket plates and weld the axle to the flat plate.
In U.S. Pat. No. 4,371,190 to VanDenberg (issued Feb. 1, 1983), a similar suspension is shown wherein a saddle plate extends between the spaced bracket plates and welds are provided between the saddle plates and the axle. Further, the axle is clamped to the saddle plates through U-bolts which are bolted to a beam housing beneath the beam or arm. U.S. Pat. No. 4,261,597 to VanDenberg (issued Apr. 14, 1981) discloses a similar structure wherein the welds can extend between the side plates and the axle as well. The VanDenberg suspensions are relatively heavy and bulky due to the many brackets, plates, beam housing and U-bolt assemblies.
U.S. Pat. No. 4,615,539 to Pierce (issued Oct. 7, 1986) discloses a suspension system wherein a bracket incorporating a complementary surface is welded to the axle. The complementary surface of the bracket extends at least 90.degree. and preferably approximately 150.degree. around the axle. The bracket is attached to the trailing arm by bushed connections.
Axle brackets are often welded to an axle by a process utilizing several welding passes to create several weld beads. The beads often end at different points along the length of the weld in order to avoid a single weak point or stress concentration point in the weld. However, the known welding processes all start at the same point at the edge of the weld bracket.
Each of the above-described suspension systems are subjected to many different forces and stresses encountered in the operation of the vehicle. The trailing arms and plates are subjected to severe shear or lateral forces. The top and bottom surfaces of the axle are subjected to severe bending stresses as a result of loading of the vehicle. The midpoint of the side of the axle is relatively free from these bending stresses. Therefore, axle brackets are usually attached to the axle at a point adjacent to the axle side-midpoint. Although generally free from these bending stresses, the weld connection between the axle brackets and axle are subject to severe torsional and shear forces as well as drive or braking torque incidental to the operation of the vehicle. These torsional stresses may cause stress cracking of the axle, the bracket or the weld, thereby necessitating costly repair or replacement of the suspension system.