Hydroformed driveshaft tube with secondary shape

Abstract

A hydroformed driveshaft tube formed using a hydroforming process is provided. The hydroformed driveshaft tube comprises a first end portion, a second end portion, and a middle portion. The middle portion is at least partially defined by a circular arc shaped surface of revolution. At least a portion of the middle portion has a diameter greater than a diameter of the first end portion and the second end portion. The middle portion is formed between the first end portion and the second end portion. The middle portion affects a critical speed and a breathing mode frequency of the hydroformed driveshaft tube. The hydroformed driveshaft tube reduces a cost of a driveshaft assembly.

What is claimed is: 
     
         1 . A hydroformed driveshaft tube, comprising:
 a first end portion;   a second end portion; and   a middle portion at least partially defined by a circular arc shaped surface of revolution and at least a portion of the middle portion having a diameter greater than a diameter of the first end portion and the second end portion, wherein the middle portion is formed between the first end portion and the second end portion and the middle portion affects a critical speed and a breathing mode frequency of the hydroformed driveshaft tube.   
     
     
         2 . The hydroformed driveshaft tube according to  claim 1 , wherein the middle portion comprises a first distension, a constriction, and a second distension, the constriction formed between the first distension and the second distension. 
     
     
         3 . The hydroformed driveshaft tube according to  claim 2 , further comprising a first tangential transition and a second tangential transition, the first tangential transition formed between the first end portion and the first distension and the second tangential transition formed between the second end portion and the second distension. 
     
     
         4 . The hydroformed driveshaft tube according to  claim 3 , further comprising a third tangential transition and a fourth tangential transition, the third tangential transition formed between the constriction and the first distension and the fourth tangential transition formed between the constriction and the second distension. 
     
     
         5 . The hydroformed driveshaft tube according to  claim 2 , wherein at least one of the first distension and the second distension is defined by the circular arc shaped surface of revolution, the circular arc shaped surface of revolution having a radius about 40 times greater than a radius of the first end portion and the second end portion. 
     
     
         6 . The hydroformed driveshaft tube according to  claim 2 , wherein a concavity of the constriction is opposite a concavity of the first distension and the second distension. 
     
     
         7 . The hydroformed driveshaft tube according to  claim 2 , wherein the constriction provides a datum to militate against tube buckling which may occur during a hydroforming process used to form the hydroformed driveshaft tube. 
     
     
         8 . The hydroformed driveshaft tube according to  claim 1 , further comprising a first transition portion, a first constriction portion, a second constriction portion, and a second transition portion, the middle portion formed between the first constriction portion and the second constriction portion. 
     
     
         9 . The hydroformed driveshaft tube according to  claim 8 , wherein the circular arc shaped surface of revolution corresponds in shape to the first transition portion, the middle portion, and the second transition portion. 
     
     
         10 . The hydroformed driveshaft tube according to  claim 9 , wherein the circular arc shaped surface of revolution has a radius about 150 times greater than a radius of the first end portion and the second end portion. 
     
     
         11 . The hydroformed driveshaft tube according to  claim 8 , wherein a concavity of the first constriction and the second constriction is opposite a concavity of the first transition portion, the middle portion, and the second transition portion. 
     
     
         12 . The hydroformed driveshaft tube according to  claim 8 , wherein the first constriction and the second constriction each provide a datum to militate against tube buckling which may occur during a hydroforming process used to form the hydroformed driveshaft tube. 
     
     
         13 . The hydroformed driveshaft tube according to  claim 8 , wherein a diameter of the first constriction and the second constriction is greater than the diameter of the first end portion and the second end portion. 
     
     
         14 . The hydroformed driveshaft tube according to  claim 1 , wherein the circular arc shaped surface of revolution has a radius about 200 times greater than a radius of the first end portion and the second end portion. 
     
     
         15 . A hydroformed driveshaft tube, comprising:
 a first end portion;   a second end portion; and   a middle portion at least partially defined by a circular arc shaped surface of revolution and at least a portion of the middle portion having a diameter greater than a diameter of the first end portion and the second end portion, the middle portion comprising a first distension, a constriction, and a second distension, wherein the middle portion is formed between the first end portion and the second end portion, the constriction is formed between the first distension and the second distension, and the middle portion affects a critical speed and a breathing mode frequency of the hydroformed driveshaft tube.   
     
     
         16 . The hydroformed driveshaft tube according to  claim 15 , further comprising a first tangential transition and a second tangential transition, the first tangential transition formed between the first end portion and the first distension and the second tangential transition formed between the second end portion and the second distension. 
     
     
         17 . The hydroformed driveshaft tube according to  claim 16 , further comprising a third tangential transition and a fourth tangential transition, the third tangential transition formed between the constriction and the first distension and the fourth tangential transition formed between the constriction and the second distension. 
     
     
         18 . The hydroformed driveshaft tube according to  claim 15 , wherein at least one of the first distension and the second distension is defined by the circular arc shaped surface of revolution, the circular arc shaped surface of revolution having a radius about 40 times greater than a radius of the first end portion and the second end portion. 
     
     
         19 . A hydroformed driveshaft tube, comprising:
 a first end portion;   a second end portion; and   a middle portion at least partially defined by a circular arc shaped surface of revolution and at least a portion of the middle portion having a diameter greater than a diameter of the first end portion and the second end portion, the middle portion comprising a first transition portion, a first constriction portion, a second constriction portion, and a second transition portion, wherein the middle portion is formed between the first constriction portion and the second constriction portion and the middle portion affects a critical speed and a breathing mode frequency of the hydroformed driveshaft tube.   
     
     
         20 . The hydroformed driveshaft tube according to  claim 19 , wherein the circular arc shaped surface of revolution corresponds in shape to the first transition portion, the middle portion, and the second transition portion.