Tube diameter expanding method and forming apparatus

Abstract

A tube diameter expanding method includes: rotating a tube having one end fixed to a turntable about a center axis of the tube; inserting a rod-like roller which extends in an axial direction of the tube into the tube from another end of the tube, and bringing the rod-like roller into contact with a forming region extending from the other end to a predetermined position of the tube; heating the forming region of the tube; cooling at least a section located near the forming region and within a non-forming region extending from the predetermined position to the one end of the tube; and moving the rod-like roller in a state of contacting the forming region of the tube, in a direction from the one end of the tube toward the other end of the tube and outward in a radial direction of the tube.

1 . A tube diameter expanding method comprising:
 rotating a tube having one end fixed to a turntable about a center axis of the tube;   inserting a rod-like roller which extends in an axial direction of the tube into the tube from another end of the tube, and bringing the rod-like roller into contact with a forming region extending from the other end to a predetermined position of the tube;   heating the forming region of the tube;   cooling at least a section located near the forming region and within a non-forming region extending from the predetermined position to the one end of the tube; and   moving the rod-like roller in a state of contacting the forming region of the tube, in a direction from the one end of the tube toward the other end of the tube and outward in a radial direction of the tube.   
     
     
         2 . The tube diameter expanding method according to  claim 1 , wherein the forming region of the tube is heated from outside of the tube. 
     
     
         3 . The tube diameter expanding method according to  claim 1 , wherein the forming region of the tube is heated by induction heating. 
     
     
         4 . The tube diameter expanding method according to  claim 1 , wherein,
 the forming region of the tube is heated by using a heater which includes a heating head that faces an inner peripheral surface or an outer peripheral surface of the tube, and   when the rod-like roller in a state of contacting the forming region of the tube is moved in the direction from the one end toward the other end of the tube and outward in the radial direction of the tube, the heating head is moved in the radial direction of the tube in synchronization with movement of the rod-like roller.   
     
     
         5 . The tube diameter expanding method according to  claim 1 , wherein
 the non-forming region of the tube is cooled by using a cooler which includes a cooling head that supplies cooler agent to an outer peripheral surface of the tube, and   when the rod-like roller in a state of contacting the forming region of the tube is moved in the direction from the one end toward the other end of the tube and outward in the radial direction of the tube, the cooling head is moved in the axial direction and the radial direction of the tube in synchronization with movement of the rod-like roller.   
     
     
         6 . The tube diameter expanding method according to  claim 1 , wherein in a state where an auxiliary roller supports at least the other end of the tube from outside in the radial direction, the rod-like roller in a state of contacting the forming region of the tube is moved in the direction from the one end toward the other end of the tube and outward in the radial direction of the tube. 
     
     
         7 . The tube diameter expanding method according to  claim 1 , wherein a tip of the rod-like roller is flat. 
     
     
         8 . The tube diameter expanding method according to  claim 1 , wherein the tube has a thickness of not less than 8 mm. 
     
     
         9 . A forming apparatus comprising:
 a turntable to which one end of a tube is fixed;   a rod-like roller which extends in an axial direction of the tube, the rod-like roller being inserted into the tube from another end of the tube and being brought into contact with a forming region extending from the other end to a predetermined position of the tube;   a heater which heats the forming region of the tube;   a cooler which cools at least a section located near the forming region and within a non-forming region extending from the predetermined position to the one end of the tube; and   a roller moving device which moves the rod-like roller in the axial direction and a radial direction of the tube.   
     
     
         10 . The forming apparatus according to  claim 9 , further comprising:
 a first temperature sensor which detects temperature of the forming region of the tube;   a second temperature sensor which detects temperature of the section located near the forming region and within the non-forming region of the tube; and   a control device which controls the heater according to temperature detected by the first temperature sensor and controls the cooler according to temperature detected by the second temperature sensor.   
     
     
         11 . The forming apparatus according to  claim 9 , wherein the heater heats the forming region by induction heating. 
     
     
         12 . The forming apparatus according to  claim 9 , wherein the heater includes a heating head which faces an inner peripheral surface or an outer peripheral surface of the tube,
 the forming apparatus further comprising a heating-head moving device which moves the heating head in the radial direction of the tube in synchronization with movement of the rod-like roller, when the roller moving device moves the rod-like roller in a state of contacting the forming region of the tube, in a direction from the one end toward the other end of the tube and outward in the radial direction of the tube.   
     
     
         13 . The forming apparatus according to  claim 9 , wherein the cooler includes a cooling head which supplies cooler agent to an outer peripheral surface of the tube,
 the forming apparatus further comprising a cooling-head moving device which moves the cooling head in the axial direction and the radial direction of the tube in synchronization with movement of the rod-like roller, when the roller moving device moves the rod-like roller in a state of contacting the forming region of the tube, in a direction from the one end toward the other end of the tube and outward in the radial direction of the tube.   
     
     
         14 . The forming apparatus according to  claim 9 , further comprising an auxiliary roller which supports at least the other end of the tube from outside in the radial direction of the tube, when the roller moving device moves the rod-like roller in a state of contacting the forming region of the tube, in a direction from the one end toward the other end of the tube and outward in the radial direction of the tube. 
     
     
         15 . The forming apparatus according to  claim 9 , wherein a tip of the rod-like roller is flat.