A press forming method for an automotive outer panel according to the present invention is a method for press forming a metal sheet 51 into an automotive outer panel 61 having a character line 63 and panel surface portions 65a and 65b by using a punch 3, a die 5, and a blank holder 7. The press forming method includes: a step of providing an elastic body 9 protruding toward the punch 3 side on a die-side forming surface portion 5b forming the panel surface portion 65a, and bringing the elastic body 9 into contact with the metal sheet 51 prior to the die 5; and a step of press forming while crushing the elastic body 9 and pressing the metal sheet 51, and the elastic body 9 is caused to protrude from the die-side forming surface portion 5b so that a frictional force of the crushed elastic body 9 and the metal sheet 51 is equal to or greater than an absolute value of a difference between tensions acting on. both sides of a portion 53 corresponding to the character line 63.

A method for press forming an automotive outer panel includes: providing an elastic body to a punch such that the elastic body abuts against a metal sheet away from a portion corresponding to a character line in the metal sheet; abutting a contact surface portion of the protruding elastic body against the metal sheet; and forming the character line with the ridgeline and the valley line by relatively moving the die toward the punch while abutting the contact surface portion against the metal sheet to deform the elastic body such that the elastic body becomes flush with the punch-side forming surface portion at a bottom dead center of forming. A protrusion amount of the elastic body from the punch-side forming surface portion is set such that the elastic body contacts the metal sheet before the ridgeline contacts the metal sheet to cause the metal sheet to become plastically deformed.

To reduce warping of vertical wall portions without causing buckling during pressing. Press-forming into a hat cross-sectional shape having one linear vertical wall portion and the other curved vertical wall portion and not having a flange portion is performed. A punch and a pad sandwiching a top sheet portion therebetween, bending blades for bend-forming the vertical wall portions, and stoppers facing the bending blades are provided. The punch is supported by a first cushion component. The bending blades each have an upper die component and a lower die component disposed facing each other in the press direction with an interval (D) equal to a set compression amount in the range of 2% or more and 6% or less of the heights of the vertical wall portions and a second cushion component interposed between the upper die component and the lower die component, maintaining the interval (D), and contractible in the press direction. The cushion pressure of the second cushion component is lower than the cushion pressure of the first cushion component and has such cushion pressure that the second cushion component does not contract during the bend-forming of the vertical wall portions.

The present invention discloses a forming device for a large thin-walled part with a curved surface, which includes a punch, a blank holder, a die, a lower die plate, a first annular sleeve and second annular sleeves. The first annular sleeve is connected with first driving oil cylinders. An inner diameter of the die is greater than an outer diameter of the punch. The first annular sleeve is arranged in a gap between the punch and the die. The second annular sleeve is arranged at the bottom of the punch. The first annular sleeve is arranged outside the second annular sleeve. The second annular sleeve is connected with second driving oil cylinders. The first driving oil cylinders and the second driving oil cylinders are connected with a hydraulic system.

The present invention discloses a forming device for a large thin-walled part with a curved surface, which includes a punch, a blank holder, a die, a lower die plate, a first annular sleeve and second annular sleeves. The first annular sleeve is connected with first driving oil cylinders. An inner diameter of the die is greater than an outer diameter of the punch. The first annular sleeve is arranged in a gap between the punch and the die. The second annular sleeve is arranged at the bottom of the punch. The first annular sleeve is arranged outside the second annular sleeve. The second annular sleeve is connected with second driving oil cylinders. The first driving oil cylinders and the second driving oil cylinders are connected with a hydraulic system.

A metal stamping tool includes a hybrid magnetorheological-nitrogen spring including a housing having an interior wall defining an interior volume. A fixed divider separates the interior volume into a nitrogen gas chamber and a magnetorheological fluid chamber. A piston extends into both the nitrogen gas chamber and the magnetorheological fluid chamber. The piston defines a magnetorheological fluid gap within the magnetorheological fluid chamber. An electric coil positioned adjacent the fluid gap to apply a magnetic field to magnetorheological fluid within the fluid gap when the electric coil is energized.

The die cushion device according to the present invention includes a first hydraulic cylinder and a second hydraulic cylinder that are independently and simultaneously controlled. When a cushion pad is pre-pressurized, pressure control is performed on the first hydraulic cylinder via a first hydraulic circuit so that a pressure in a lower chamber of the first hydraulic cylinder is pre-pressurized to a preset pressure, and position control is simultaneously performed on the second hydraulic cylinder via a second hydraulic circuit so that the cushion pad is held in the die cushion standby position. A force with which the first hydraulic cylinder moves the cushion pad upward is balanced with a force with which the second hydraulic cylinder moves the cushion pad downward (a force for holding the die cushion standby position).

The die cushion device according to the present invention includes a first hydraulic cylinder and a second hydraulic cylinder that are independently and simultaneously controlled. When a cushion pad is pre-pressurized, pressure control is performed on the first hydraulic cylinder via a first hydraulic circuit so that a pressure in a lower chamber of the first hydraulic cylinder is pre-pressurized to a preset pressure, and position control is simultaneously performed on the second hydraulic cylinder via a second hydraulic circuit so that the cushion pad is held in the die cushion standby position. A force with which the first hydraulic cylinder moves the cushion pad upward is balanced with a force with which the second hydraulic cylinder moves the cushion pad downward (a force for holding the die cushion standby position).

A stamping machine configured to shape a sheet material including an upper binder including first teeth, a lower binder including second teeth, and a punch. A first cylinder is positioned between a lower binder and a support surface. A second cylinder is positioned between the upper binder and the lower binder. A cushion pin is positioned at the support surface that is configured to contact and control movement of the lower binder relative to the punch. A force exerted by the second cylinder is greater than that exerted by the first cylinder, and the force exerted by the cushion pin is greater than that exerted by the second cylinder. The first and second cylinders and the cushion pin are used to control when the first and second teeth are permitted to engage the sheet material, which assists in preventing or minimizing spring back of the sheet material through post-stretching.

A press forming method for an automotive outer panel according to the present invention is a method for press forming a metal sheet 51 into an automotive outer panel 61 having a character line 63 and panel surface portions 65a and 65b by using a punch 3, a die 5, and a blank holder 7. The press forming method includes: a step of providing an elastic body 9 protruding toward the punch 3 side on a die-side forming surface portion 5b forming the panel surface portion 65a, and bringing the elastic body 9 into contact with the metal sheet 51 prior to the die 5; and a step of press forming while crushing the elastic body 9 and pressing the metal sheet 51, and the elastic body 9 is caused to protrude from the die-side forming surface portion 5b so that a frictional force of the crushed elastic body 9 and the metal sheet 51 is equal to or greater than an absolute value of a difference between tensions acting on both sides of a portion 53 corresponding to the character line 63.