Patent Application
20090200786
The present invention relates generally to a vehicular chassis, and, more particularly, to joining a cross member to a frame rail, such as a vehicle frame.
The chassis of a motor vehicle includes two laterally spaced, longitudinally directed frame members, on which the suspension, engine and powertrain are supported. The frame rails are in the form of a closed or open section beam having upper and lower flanges or caps, and one or two webs interconnecting the flanges. The frame rails are interconnected by laterally directed cross members, which are secured to the web of each of the frame rails. The cross members are usually cylindrical having a circular or noncircular cross section, which is usually tubular but may be a non-tubular solid, such as a rod. Generally, the frame rails and the cross members are formed of sheet steel.
The cross members may be joined to the web of the frame rails by punching or drilling a hole in the web, inserting the cross member in the hole, and securing the frame rail to the cross member with a weld at the periphery of the hole and cross member. A joint formed in this way has relatively high stress in the weld, which can affect durability.
To enhance durability of the joint, a collar may be welded to the surface of the frame rail surrounding the hole. The cross member is inserted in the hole and through the collar, and the frame rail is secured to the cross member with a weld at the periphery of the collar and the cross member. Although the welded collar provides additional structural continuity between the frame rail and the cross member by adding a third part to the joint, the weld between the collar and frame rail requires additional space, restricting the location of the cross member. The additional collar increases the costs of components, tooling and the welding operation.
A need exists for a joint that provides improved service durability, has a minimum number of parts and requires only a compact space that may extend into a transition radius between the caps and web of the frame rail.
An embodiment contemplates a welded joint for connecting a cross member and a web. The web has an extruded hole that extends through a thickness of the web and conforms to a cross sectional shape of the cross member. A collar surrounding the hole is formed from material extruded from the web in a direction such that the collar extends along the cross member and away from the web. The cross member extends through the hole and into the collar. A weld mutually connects the collar and the cross member.
An advantage of an embodiment is the excellent service durability of a welded joint that incorporates a collar extruded from one of the members connected by the joint. The joint requires no additional component to transition structural load between the joined members, such as a preformed collar. The joint is completed by welding the joined members mutually, thereby eliminating need for a weld between a preformed collar and one of the joined members.
Use of a preformed collar would require additional space to weld the collar to the frame rail. By avoiding the need for a preformed collar, the cross member can be located closer to the tangent of a radius formed between the caps and web of the frame rail.
Referring to
The frame rails 12 are interconnected by a laterally directed cross member 20, which is secured to the web 18 of each of the frame rails. The cross member 20 is usually cylindrical having a circular or noncircular cross section, which is usually tubular. Generally, the frame rails 12 and the cross member 20 are formed of low alloy, sheet steel. The cross member 20 extends laterally and substantially perpendicular to the plane of the web 18, or it is inclined with respect to the web.
A joint for connecting the web 18 and cross member 20 includes a hole 22 formed directly in the web. The material of the web 20 is extruded in the direction of the cross member 20, thereby forming an extruded collar or flange 24 that surrounds the hole 22 and extends away from the web. The thickness 26 of the web material surrounding the extruded hole 22 faces the cross member 20.
Referring now to
Referring now to
After the collar 24 is extruded, the cross member 20 is inserted into the hole 22 and through the extruded collar 24, extending about 10.0 mm. past the collar. Two seam welds 30, 32 secure the extruded collar 24 to the cross member 20. Welds 30, 32 are made using a gas metal arc weld (GMAW), frequently referred to as a MIG weld, which is a commonly used, high deposition rate welding process in which wire is continuously fed from a spool.
The extrusion process for forming hole 22 and collar 24 is described with reference to
The extrusion operation improves the material properties in the radius 32 of the extruded collar 24, where typically the highest stress and fatigue damage occurs in this type of joint. Cold working of the extruded collar 24 at the radius 44 improves the strength and durability of the joint.
Without an extrusion collar 24, the highly stressed area of the joint would be in the weld and the heat-affected zone where the web 18 is welded to the cross member 20. That weld would act as a crack initiator as well as a stress concentration, affecting the durability of a joint without an extruded collar 24. A joint having the extruded collar 24 as shown in
While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
