Press forming method and press forming tool
A press forming method according to the present invention includes: a first forming step of forming the press formed part by using the first press forming tool having a line length in the cross-sectional direction of the joining portion contacting with a flange portion subjected to stretch flange deformation or a flange portion subjected to shrink flange deformation is a line length L 1 in the cross-sectional direction that is shorter than a line length L 2 , where the line length L 2 is a line length in a cross-sectional direction of the joining portion of the second press forming tool for making the product shape; and a second forming step of forming the press formed part in the product shape by crash forming by using the second press forming tool in which the line length in the cross-sectional direction of the joining portion is L 2.
1. A press forming method for forming a press formed part having a product shape that has a groove-shaped portion extending in a longitudinal direction and includes a flange portion curved along the longitudinal direction on at least one of a pair of side wall portions defining the groove-shaped portion, using a first press forming tool and a second press forming tool each including a side wall forming portion, a flange forming portion, and a joining portion that joins the flange forming portion to the side wall forming portion, the press forming method comprising:
a first forming process of forming the press formed part in an intermediate shape by using the first press forming tool having a line length L 1 which is a line length in the cross-sectional direction of the joining portion contacting with a flange portion of the intermediate shape which is subjected to stretch flange deformation or a flange portion of the intermediate shape which is subjected to shrink flange deformation, where the line length L 1 is shorter than a line length L 2 , where the line length L 2 is a line length in a cross-sectional direction of the joining portion of the second press forming tool for making the product shape, in order to make a line length of the flange portion of the intermediate shape which is subjected to the stretch flange deformation in a longitudinal direction longer than a line length of the flange portion of the product shape or to make a line length of the flange portion of the intermediate shape which is subjected to the shrink flange deformation in the longitudinal direction shorter than the line length of the flange portion of the product shape; and
a second forming process of forming the press formed part from the intermediate shape into the product shape by crash forming by using the second press forming tool in which the line length in the cross-sectional direction of the joining portion is L 2 .
2. The press forming method according to claim 1 , wherein the first forming process and the second forming process are applied to one of the pair of side wall portions.
3. The press forming method according to claim 1 , wherein the first forming process and the second forming process are applied to both of the pair of side wall portions.
4. The press forming method according to claim 1 , further comprising forming punch bottom portion of the press formed part by performing the first forming process and the second forming process with a portion of the press formed part corresponding to the punch bottom portion pressed with a pad.
5. The press forming method according to claim 1 , wherein the joining portions of the first press forming tool and the second press forming tool have an arc cross-sectional shape.
6. The press forming method according to claim 1 , wherein the joining portion of the first press forming tool has an arc cross-sectional shape, and the joining portion of the second press forming tool has a chamfered cross-sectional shape produced by chamfering an arc shape.
7. A press forming tool used for a press forming method for forming a press formed part having a product shape that has a groove-shaped portion extending in a longitudinal direction and includes a flange portion that is curved along the longitudinal direction on at least one of a pair of side wall portions defining the groove-shaped portion and subjected to stretch flange deformation and/or shrink flange deformation, through a first forming process and a second forming process, the press forming tool comprising:
a first press forming tool for the first forming process and a second press forming tool for the second forming process, wherein
the first press forming tool and the second press forming tool each include a side wall forming portion, a flange forming portion, and a joining portion that joins the flange forming portion to the side wall forming portion, and
a line length in a cross-sectional direction of the joining portion of the first press forming tool is set to be shorter than a line length in a cross-sectional direction of the joining portion of the second press forming tool, the joining portion of the first press forming tool being in contact with a flange portion subjected to stretch flange deformation or a flange portion subjected to shrink flange deformation in the first press forming tool.
8. The press forming tool according to claim 7 , wherein the joining portions of the first press forming tool and the second press forming tool have an arc cross-sectional shape.
9. The press forming tool according to claim 7 , wherein the joining portion of the first press forming tool has an arc cross-sectional shape, and the joining portion of the second press forming tool has a chamfered cross-sectional shape produced by chamfering an arc shape.