Method of manufacturing pipe

Abstract

A method of manufacturing a pipe extending along an axis of the pipe includes forming a blank material into a U-shaped member that extends along the axis and has a cross-section of U-shape, and forming the U-shaped member into a shape of the pipe. The pipe includes a large-diameter portion, a small-diameter portion, and a gradually-reduced-diameter portion. The gradually-reduced-diameter portion connects the large-diameter portion and the small-diameter portion to each other. In the method of manufacturing the pipe, at least one bead extending along the axis of the pipe is formed in a part, of the blank material or the U-shaped member, that corresponds to the gradually-reduced-diameter portion.

What is claimed is: 
     
         1 . A method of manufacturing a pipe extending along an axis of the pipe, the method comprising:
 forming a blank material, which is a metal plate-shaped member, into a U-shaped member, the U-shaped member extending along the axis and having a cross-section, orthogonal to the axis, of U-shape;   forming the U-shaped member into a shape of the pipe, the pipe including:
 a large-diameter portion having the cross-section with a relatively large diameter; 
 a small-diameter portion having the cross-section with a relatively small diameter; and 
 a gradually-reduced-diameter portion connecting the large-diameter portion and the small-diameter portion to each other, a diameter of the cross-section of the gradually-reduced-diameter portion being gradually reduced toward the small-diameter portion; and 
   forming at least one bead in a part, of the blank material or the U-shaped member, that corresponds to the gradually-reduced-diameter portion, the at least one bead extending along the axis of the pipe.   
     
     
         2 . The method of manufacturing a pipe according to  claim 1 ,
 wherein the U-shaped member has a first end portion including a first end of the cross-section of the U-shaped member and a second end portion including a second end of the cross-section of the U-shaped member,   wherein the method further comprises:   bending the first end portion and the second end portion of the U-shaped member so that the first end and the second end come closer to each other, and   wherein the at least one bead is formed in the first end portion and/or the second end portion when bending the first end portion and the second end portion.   
     
     
         3 . The method of manufacturing a pipe according to  claim 1 ,
 wherein the pipe further includes a butted portion where a first end and a second end of the cross-section of the U-shaped member are joined together, and   wherein at least two beads are formed in the part, of the blank material or the U-shaped member, that corresponds to the gradually-reduced-diameter portion, and when the U-shaped member is formed into the shape of the pipe, two beads of the at least two beads are arranged in the gradually-reduced-diameter portion so as to have the butted portion therebetween.   
     
     
         4 . The method of manufacturing a pipe according to  claim 3 ,
 wherein, when the U-shaped member is formed into the shape of the pipe, the two beads extend along the butted portion in a periphery of the butted portion in the gradually-reduced-diameter portion.   
     
     
         5 . The method of manufacturing a pipe according to  claim 3 ,
 wherein, when the U-shaped member is formed into the shape of the pipe, the two beads pass a boundary of the gradually-reduced-diameter portion with the large-diameter portion in the pipe or pass a vicinity of the boundary.   
     
     
         6 . The method of manufacturing a pipe according to  claim 1 ,
 wherein, when the U-shaped member is formed into the shape of the pipe, the at least one bead passes a boundary of the gradually-reduced-diameter portion with the large-diameter portion in the pipe or passes a vicinity of the boundary.   
     
     
         7 . The method of manufacturing a pipe according to  claim 1 ,
 wherein the pipe further includes a butted portion where a first end and a second end of the cross-section of the U-shaped member are joined together, and   wherein, when the U-shaped member is formed into the shape of the pipe, the at least one bead extends along the butted portion in a periphery of the butted portion in the gradually-reduced-diameter portion.   
     
     
         8 . The method of manufacturing a pipe according to  claim 1 ,
 wherein the pipe is to be mounted in a vehicle.   
     
     
         9 . The method of manufacturing a pipe according to  claim 8 ,
 wherein the pipe is to be used in an instrument panel reinforcement of the vehicle.