Hollow spring member

Abstract

On an end portion of a hollow rod, which is a material of a hollow coil spring, a terminal sealed portion is formed. The terminal sealed portion has a rotationally symmetric shape in which an axis passing through the center of the rod is a symmetric axis. The terminal sealed portion includes an end wall portion, and a distal-end-center closure portion formed on the axis. In the distal-end-center closure portion, a distal end opening portion of the spin-formed rod is joined together and formed as an integral part. On the axis at the inner surface of the end wall portion, a recess having a rotationally symmetric shape in which the axis is the symmetric axis is formed. A thickness of the recess of the end wall portion is reduced toward the axis.

What is claimed is: 
     
         1 . A hollow spring member which is constituted of a hollow rod, and includes a terminal sealed portion at an end portion of the rod,
 the terminal sealed portion having a rotationally symmetric shape in which an axis passing through a center of the rod is a symmetric axis, and including:   an end wall portion including an end face;   a distal-end-center closure portion existing on the axis at a center of the end wall portion; and   a recess formed on an inner surface of the end wall portion, and having a rotationally symmetric shape in which the axis is the symmetric axis.   
     
     
         2 . The hollow spring member of  claim 1 , wherein a thickness of the recess of the end wall portion is reduced toward the axis, and a center of the recess is located on the axis. 
     
     
         3 . The hollow spring member of  claim 1 , wherein the hollow spring member is constituted of the hollow rod formed into a helical shape, and has a shape of a coil spring. 
     
     
         4 . The hollow spring member of  claim 1 , wherein the hollow spring member is constituted of the hollow rod including a torsion portion and an arm portion, and has a shape of a vehicle stabilizer. 
     
     
         5 . The hollow spring member of  claim 1 , wherein the hollow spring member is constituted of the hollow rod including mounting portions on both ends of the hollow rod, and has a shape of a torsion rod.