Processing method of tube body, manufacturing method of cylinder device and cylinder device manufactured by the same

Abstract

There is provided a processing method of a tube body comprising the steps of a tube-expanding step wherein a base tube is partially retained with a chuck unit having a rotational function, and a mandrel is pressed in to an end portion of the base tube so as to expand the end portion of the base tube; and a rotation ironing step wherein the chuck unit rotates the base tube together with the mandrel a roller die is pressed against an outer-periphery surface of the end portion of the base tube and the roller die is moved with respect to the base tube and in an axial direction thereof so as to deform an inner periphery surface of the end portion of the base tube into a shape corresponding to an external shape of the mandrel.

1 . A processing method of a tube body comprising the steps of
 a tube-expanding step wherein a base tube is partially retained with a chuck unit having a rotational function, and a mandrel is pressed in to an end portion of the base tube so as to expand the end portion of the base tube; and   a rotation ironing step wherein the chuck unit rotates the base tube together with the mandrel a roller die is pressed against an outer-periphery surface of the end portion of the base tube and the roller die is moved with respect to the base tube and in an axial direction thereof so as to deform an inner-periphery surface of the end portion of the base tube into a shape corresponding to an external shape of the mandrel.   
   
   
       2 . A processing method of a tube body according to  claim 1 , wherein thickness of the end portion of the base tube is reduced in the rotation ironing step. 
   
   
       3 . A processing method of a tube body according to  claim 2 , wherein the thickness of the end portion of the base tube is reduced in the rotation ironing step until an external diameter of the end portion of the base tube becomes identical with an external diameter of the base tube. 
   
   
       4 . A processing method of a tube body according to  claim 2 , wherein the roller die is moved toward a tip end portion of the base tube in an axial direction during the rotation ironing step. 
   
   
       5 . A processing method of a tube body according to  claim 3 , wherein the roller die is moved toward a tip end portion of the base tube in an axial direction during the rotation ironing step. 
   
   
       6 . A processing method of a tube body according to  claim 4 , wherein the mandrel includes: a press-in portion pressed into the base tube; and an abutting portion having a larger diameter than the press-in portion and made to abut to the tip end portion of the base tube due to the rotation ironing step. 
   
   
       7 . A processing method of a tube body according to  claim 5 , wherein the mandrel includes: a press-in portion pressed into the base tube; and an abutting portion having a larger diameter than the press-in portion and made to abut to the tip end portion of the base tube due to the rotation ironing step. 
   
   
       8 . A processing method of a tube body according to  claim 6 , wherein the abutting portion is formed into a tapered shape, the diameter of which becomes wider in the axial direction away from the press-in portion. 
   
   
       9 . A processing method of a tube body according to  claim 7 , wherein the abutting portion is formed into a tapered shape, the diameter of which becomes wider in the axial direction away from the press-in portion. 
   
   
       10 . A processing method of a tube body according to  claim 1 , further comprising an end cutting step in which excess material of the end portion of the base tube is cut off following the rotation ironing step. 
   
   
       11 . A processing method of a tube body according to  claim 8 , further comprising an end cutting step in which excess material of the end portion of the base tube is cut off following the rotation ironing step. 
   
   
       12 . A processing method of a tube body according to  claim 9 , further comprising an end cutting step in which excess material of the end portion of the base tube is cut off following the rotation ironing step. 
   
   
       13 . A processing method of a tube body according to  claim 1 , wherein the press-in portion of the mandrel being pressed into the base tube is a multi-stepped formation including at least two steps, the multi-stepped formation gradually becoming wider from an insertion end of the mandrel. 
   
   
       14 . A processing method of a tube body according to  claim 1 , further comprising a step of decreasing an external diameter of the end portion of the base tube before the mandrel is pressed in. 
   
   
       15 . A processing method of a tube body according to  claim 1 , further comprising a cutting step for cutting an outer periphery of the end portion of the base tube following the rotation ironing step. 
   
   
       16 . A manufacturing method of a cylinder device comprising the steps of:
 a manufacturing step of manufacturing a cylinder by the processing method of a tube body according to  claim 1 ;   an assembling step of assembling interior parts including a piston, a piston rod and a rod guide into the cylinder; and   a curling process of curling a tip end portion of the cylinder so as to prevent the interior parts from falling off.   
   
   
       17 . A cylinder device comprising:
 a cylinder;   a rod adapted to be compressed into or extended from one end of the cylinder;   a rod guide inserted into the one end of the cylinder so as to support the rod; and   a curled portion formed by curling a tip end portion of the cylinder so as to prevent the rod guide from falling off from the cylinder,   wherein the cylinder is formed by pressing a mandrel into an end portion of a base tube, and pressing a roller die against the base tube so as to deform an inner-periphery surface of the end portion of the base tube along an outer-periphery surface of the mandrel.   
   
   
       18 . A cylinder device comprising:
 a rod adapted to be compressed into or extended from one end of the cylinder;   a rod guide inserted into the one end of the cylinder so as to support the rod; and   a curled portion formed by curling a tip end portion of the cylinder so as to prevent the rod guide from falling off from the cylinder,   wherein a thickness reduction rate of the one end of the cylinder is 50% or less.   
   
   
       19 . A cylinder device according to  claim 17 , wherein the curled portion is a fully curled portion in which the whole circumference is curled. 
   
   
       20 . A cylinder device according to  claim 18 , wherein the curled portion is a fully curled portion in which the whole circumference is curled. 
   
   
       21 . A cylinder device according to  claim 17 , wherein the cylinder device is a shock absorber for a vehicle suspension strut. 
   
   
       22 . A cylinder device according to  claim 18 , wherein the cylinder device is a shock absorber for a vehicle suspension strut.