Die cushion device

Patent metadata

Field	Value
Publication number	US-12023723-B2
Application number	US-202117553418-A
Country	US
Kind code	B2
Filing date	Dec 16, 2021
Priority date	Dec 18, 2020
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

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).

First claim

What is claimed is:

1. A die cushion device comprising:
a first hydraulic cylinder configured to support a cushion pad and generate a die cushion force on the cushion pad in a case where a slide of a press machine is moved downward;
a first hydraulic circuit configured to drive the first hydraulic cylinder;
a first pressure commander configured to output a first pressure command indicating a die cushion pressure corresponding to the die cushion force;
a first pressure detector configured to detect a pressure applied to a lower chamber of the first hydraulic cylinder;
a first controller configured to control the first hydraulic circuit based on the first pressure command and the pressure detected by the first pressure detector, in such a manner that the pressure applied to the lower chamber of the first hydraulic cylinder matches a pressure corresponding to the first pressure command;
a second hydraulic cylinder configured to support the cushion pad and move the cushion pad in an up-and-down direction;
a second hydraulic circuit configured to drive the second hydraulic cylinder;
a die cushion position commander configured to output a die cushion position command indicating a position of the cushion pad;
a die cushion position detector configured to detect a position of the cushion pad; and
a second controller configured to control the second hydraulic circuit based on the die cushion position command and the position of the cushion pad detected by the die cushion position detector, in such a manner that the position of the cushion pad matches a position corresponding to the die cushion position command,
wherein:
the first pressure commander outputs a second pressure command for pre-pressurizing the lower chamber of the first hydraulic cylinder to a preset pressure before press forming;
the die cushion position commander outputs a first die cushion position command for causing the cushion pad to stand by at a die cushion standby position before press forming;
the first controller controls the first hydraulic circuit based on the second pressure command and the pressure detected by the first pressure detector, to pre-pressurize the lower chamber of the first hydraulic cylinder to a pressure corresponding to the second pressure command; and
the second controller controls the second hydraulic circuit based on the first die cushion position command, to cause the cushion pad to stand by at the die cushion standby position.

2. The die cushion device according to claim 1 , wherein
pressure control on the first hydraulic cylinder by the first controller and the first hydraulic circuit is performed simultaneously with position control on the second hydraulic cylinder by the second controller and the second hydraulic circuit.

3. The die cushion device according to claim 1 , wherein
the first hydraulic circuit includes:
a die cushion pressure generation line connected to the lower chamber of the first hydraulic cylinder;
a system pressure line to which an upper chamber of the first hydraulic cylinder and a first accumulator for accumulating a hydraulic fluid with a first system pressure are individually connected;
a first hydraulic pump/motor connected between the die cushion pressure generation line and the system pressure line; and
a first servomotor connected to a rotating shaft of the first hydraulic pump/motor, and
the first controller controls a torque of the first servomotor based on the first pressure command or the second pressure command, and the pressure detected by the first pressure detector.

4. The die cushion device according to claim 1 , wherein
the first hydraulic circuit is a hydraulic closed circuit including:
a die cushion pressure generation line connected to the lower chamber of the first hydraulic cylinder;
a system pressure line to which a first accumulator configured to accumulate a hydraulic fluid with a first system pressure is connected;
a logic valve configured to be pilot-operated, the logic valve having an A port connected to the die cushion pressure generation line and a B port connected to the system pressure line;
a first solenoid valve configured to open and close a flow path between the die cushion pressure generation line and the system pressure line;
a pressure generator configured to generate a pilot pressure acting on a pilot port of the logic valve; and
a first hydraulic line connecting the pressure generator and the die cushion pressure generation line, and
the first controller is further configured to:
control the pilot pressure based on the first pressure command or the second pressure command, and the pressure detected by the first pressure detector; and
control a pressure in the lower chamber of the first hydraulic cylinder, which is a pressure on a side of the A port of the logic valve so as to correspond to the first pressure command or the second pressure command.

5. The die cushion device according to claim 4 , wherein a throttle is disposed in the first hydraulic line.

6. The die cushion device according to claim 4 , wherein the first hydraulic circuit has a second hydraulic line connecting an upper chamber of the first hydraulic cylinder and the system pressure line.

7. The die cushion device according to claim 4 , wherein the first hydraulic circuit has a second solenoid valve configured to selectively cause the first system pressure or the pilot pressure to act on the pilot port of the logic valve.

8. The die cushion device according to claim 4 , wherein
the pressure generator includes:
a hydraulic pump disposed between the system pressure line and the pilot port of the logic valve; and
a third servomotor connected to a rotating shaft of the hydraulic pump, and
the first controller controls a torque of the third servomotor based on the first pressure command or the second pressure command and the pressure detected by the first pressure detector, to control the pilot pressure.

9. The die cushion device according to claim 1 , wherein:
the die cushion standby position is a position above an impact position where press forming starts;
the die cushion position commander outputs the first die cushion position command, and subsequently outputs a second die cushion position command for pre-accelerating the cushion pad before a position of the slide reaches the impact position; and
the second controller controls the second hydraulic circuit based on the second die cushion position command, to pre-accelerate the cushion pad during a period over which the cushion pad reaches the impact position from the die cushion standby position.

10. The die cushion device according to claim 1 , further comprising:
a second pressure commander configured to output a third pressure command indicating a preset third pressure; and
a second pressure detector configured to detect a pressure in a lower chamber of the second hydraulic cylinder, wherein
the second controller controls the second hydraulic circuit during press forming based on the third pressure command and the pressure detected by the second pressure detector, in such a manner that the lower chamber of the second hydraulic cylinder has the third pressure corresponding to the third pressure command.

11. The die cushion device according to claim 10 , wherein the third pressure command is a pressure command corresponding to an auxiliary die cushion force that assists a main die cushion force generated by the first hydraulic cylinder, or a pressure command for making a die cushion force generated by the second hydraulic cylinder zero.

12. The die cushion device according to claim 1 , wherein
the die cushion position commander outputs a third die cus

Assignees

• Aida Eng Ltd

Inventors

• Kondo Tadahiro

Classifications

• B30B15/16

  Control arrangements for fluid-driven presses (pumps per se F04; hydraulic accumulators per se F15B; valves per se F16K; control devices in general G05) · CPC title

• B21D24/14

  pneumatically or hydraulically · CPC title

• B21D24/08

  Pneumatically or hydraulically loaded blank holders · CPC title

• B30B15/163

  for accumulator-driven presses · CPC title

• B30B15/08

  Accessory tools, e.g. knives; Mountings therefor · CPC title