Press forming method

Abstract

A press forming method of press forming a press forming part that includes a top portion, a side wall portion continuous from the top portion via a punch shoulder, and a flange portion continuous from the side wall portion via a die shoulder, the press forming part having a curved portion curved in a recessed manner in a top view, the press forming method includes: making a bending radius of the die shoulder in the curved portion increased from an end side toward a middle portion of the curve.

1 - 6 . (canceled) 
     
     
         7 . A press forming method of press forming a press forming part that includes a top portion, a side wall portion continuous from the top portion via a punch shoulder, and a flange portion continuous from the side wall portion via a die shoulder, the press forming part having a curved portion curved in a recessed manner in a top view, the press forming method comprising:
 making a bending radius of the die shoulder in the curved portion increased from an end side toward a middle portion of the curve.   
     
     
         8 . The press forming method according to  claim 7 , wherein a minimum bending radius of the die shoulder is made smaller than a bending radius of the punch shoulder. 
     
     
         9 . The press forming method according to  claim 7 , wherein a portion of shape that restrains rotational motion, which restrains a rotational motion of a blank in a press forming process, is formed on the top portion on the end side of the curve. 
     
     
         10 . The press forming method according to  claim 8 , wherein a portion of shape that restrains rotational motion, which restrains a rotational motion of a blank in a press forming process, is formed on the top portion on the end side of the curve. 
     
     
         11 . The press forming method according to  claim 7 , wherein a flange width of the flange portion in the curved portion is larger in the middle portion than on the end side of the curve. 
     
     
         12 . The press forming method according to  claim 8 , wherein a flange width of the flange portion in the curved portion is larger in the middle portion than on the end side of the curve. 
     
     
         13 . The press forming method according to  claim 9 , wherein a flange width of the flange portion in the curved portion is larger in the middle portion than on the end side of the curve. 
     
     
         14 . The press forming method according to  claim 10 , wherein a flange width of the flange portion in the curved portion is larger in the middle portion than on the end side of the curve. 
     
     
         15 . The press forming method according to  claim 7 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         16 . The press forming method according to  claim 8 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         17 . The press forming method according to  claim 9 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         18 . The press forming method according to  claim 10 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         19 . The press forming method according to  claim 11 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         20 . The press forming method according to  claim 12 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         21 . The press forming method according to  claim 13 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         22 . The press forming method according to  claim 14 , wherein a blank used for the press forming of the press forming part is a metal sheet having tensile strength of a 440 MPa-grade to a 1600 MPa-grade. 
     
     
         23 . A press forming method of further performing, with a press forming part press formed by the press forming method according to  claim 7  being a pre-formed part, press forming of the pre-formed part into a target shape, the press forming method comprising:
 making, in the pre-formed part, a bending radius of the die shoulder in the middle portion of the curved portion larger than the target shape.