Vehicle structural components made from tubular members and method therefor

Abstract

The invention provides rear suspension structures and engine cradles involving tubular components. The tubular components have variable wall thickness along the length for reducing materials required. The tubular components also have mechanical properties varying along the length of the tubular components, to meet the requirements on strength and dynamic and static loads. The weight of the tubular components can be further reduced by appropriately varying the wall thickness and mechanical properties along the length of the tubular components.

1 . A cross member for a rear suspension assembly, the cross member comprising: 
 a unitary tubular member, the tubular member having a variable wall thickness along its length;    the tubular member having a generally elongated center portion, the center portion defining a longitudinal axis along the center portion;    the tubular member including a pair of end portions and a pair of intermediate sections each formed between the center portion and one of the end portions, said pair of intermediate sections integrally connecting the end portions to the center portion;    each of the end portions being displaced from and generally parallel with the longitudinal axis,    wherein the wall thickness at the end portions is smaller than the wall thickness at the intermediate sections.    
   
   
       2 . The cross member of  claim 1 , wherein the wall thickness is larger at the center portion than at the bend portions.  
   
   
       3 . The cross member of  claim 1 , wherein the wall thickness is smaller at the center portion than at the bend portions.  
   
   
       4 . An engine support structure for supporting an engine of a vehicle, the engine support structure comprising: 
 a pair of side rails spaced from each other; and    a front cross member and a rear cross member spaced from the front member, the front and rear cross members joining the side rails to form a general quadrilateral shape,    wherein each of the side rails is formed from a unitary tubular member, the unitary tubular member having a variable wall thickness along its length, the wall thickness monotonically increasing along the unitary tubular member in a forward direction in a substantial portion of the unitary tubular member.    
   
   
       5 . The engine support structure of  claim 4 , wherein the substantial portion extends between the rear cross member and the front cross member.  
   
   
       6 . A method of making a unitary tubular component from a metallic blank tube, the tubular component having a variable wall thickness and a desired shape, the method comprising the steps of: 
 placing the blank tube in a die and mandrel assembly,    passing the blank tube through the die and mandrel assembly to form a tubular blank, the tubular blank having a wall thickness varying along its length, and    placing the tubular blank in a forming die and forming the tubular blank into the desired shape.    
   
   
       7 . The method of  claim 6 , further comprising the step of: 
 heat treating the tubular blank at selected locations to adjust mechanical properties of material thereat.    
   
   
       8 . The method of  claim 7 , wherein the tubular blank is heat treated at a location where a bend is formed.  
   
   
       9 . The method of  claim 7 , wherein the tubular blank is heat treated at a location where the wall thickness is reduced.