Patent ID: 9468971
Filing Date: 2016-10-18
CPC Classification: B21C,B21D,B21K

Claim Text:
1. A press forming method which applies press forming to a cup-shaped workpiece having a cup longitudinal wall portion, a cup bottom portion, and a cup shoulder portion connecting the cup longitudinal wall portion and the cup bottom portion, by using a press forming device, wherein the press forming device includes an inner punch, an annular outer punch, and a die whose center axes are disposed on the same axis, the outer punch being disposed so as to be apart from the inner punch in a radial direction perpendicular to the center axis by a first space which is larger than a plate thickness of the cup longitudinal wall portion, and the die being disposed to face the inner punch in a direction of the center axis, and an inner peripheral surface of the outer punch has, on a side thereof closer to the die in terms of the center axis direction, a punch shoulder portion widening as the punch shoulder portion goes toward the die, the method comprising: a first step of sandwiching the cup bottom portion by the inner punch and the die while an outer peripheral surface of the inner punch and an inner peripheral surface of the cup longitudinal wall portion are apart from each other by a second space; and a second step of performing drawing to radially reduce the cup longitudinal wall portion by pushing the cup longitudinal wall portion toward the outer peripheral surface of the inner punch by the outer punch while moving the outer punch relatively to the inner punch and the die along the center axis to make the outer punch abut on the cup longitudinal wall portion from the punch shoulder portion, thereby making a surplus material of the workpiece flow into the cup shoulder portion to thicken the cup shoulder portion.