Stabilizer and method of manufacturing the same

A manufacturing method of manufacturing a stabilizer by increasing a diameter and a thickness of an end portion of a raw tube using a die and a punch,

• the raw tube extending in an axial direction,
• the die comprising a recessed portion having a stepped shape with an inside diameter that changes in the axial direction,
• the punch comprising a large-diameter portion having an outside diameter greater than an inside diameter of the raw tube,
• the recessed portion comprising:
• a small-diameter recessed portion having an inside diameter equal to an outside diameter of the raw tube;
• a medium-diameter recessed portion having an inside diameter greater than the inside diameter of the small-diameter recessed portion;
• and
• a large-diameter recessed portion having an inside diameter greater than the inside diameter of the medium-diameter recessed portion and greater than a value obtained by adding a value that is twice a wall thickness of the raw tube to the outside diameter of the large-diameter portion of the punch,
• the manufacturing method comprising:
• a diameter increasing step of increasing a diameter of a workpiece as the raw tube by moving the punch forward in the axial direction to insert the punch into an inner circumferential side of the workpiece from an end of the workpiece in a state in which an outer circumferential portion of the workpiece is held by the small-diameter recessed portion of the die;
• and
• a diameter-and-thickness increasing step of increasing the diameter and a thickness of the workpiece by deforming the workpiece by applying a pressing force to the workpiece in the axial direction from the end of the workpiece.

A manufacturing method of manufacturing a stabilizer by increasing a diameter and a thickness of an end portion of a raw tube using a die, a first punch, and a second punch,

• the raw tube extending in an axial direction,
• the die comprising a recessed portion having a stepped shape with an inside diameter that changes in the axial direction,
• the first punch comprising a large-diameter portion having an outside diameter greater than an inside diameter of the raw tube,
• the second punch having a stepped shape with an outside diameter that changes in the axial direction, the second punch comprising:
• a first large-diameter portion having an outside diameter less than or equal to the outside diameter of the large-diameter portion of the first punch;
• and a second large-diameter portion having an outside diameter greater than the outside diameter of the large-diameter portion of the first punch,
• the recessed portion comprising:
• a small-diameter recessed portion having an inside diameter equal to an outside diameter of the raw tube;
• a medium-diameter recessed portion having an inside diameter greater than the inside diameter of the small-diameter recessed portion;
• and
• a large-diameter recessed portion having an inside diameter greater than the inside diameter of the medium-diameter recessed portion and greater than a value obtained by adding a value that is twice a wall thickness of the raw tube to the outside diameter of the large-diameter portion of the first punch,
• the manufacturing method comprising:
• a two-step diameter increasing step of increasing a diameter of an end portion of a workpiece as the raw tube so as to form two step portions on the end portion of the workpiece by moving the second punch forward in the axial direction to insert the second punch into an inner circumferential side of the workpiece in a state in which an outer circumferential portion of the workpiece is held by the small-diameter recessed portion of the die;
• a replacing step of moving the second punch backward to an outside of the workpiece and moving the first punch forward to insert the first punch into the workpiece from an end of the workpiece;
• and
• a thickness increasing step of increasing a thickness of the workpiece by deforming the workpiece by applying a pressing force to the workpiece in the axial direction from the end of the workpiece.