Patent ID: 8757056

Claim:
A die cushion device for a press machine, the die cushion device comprising: a hydraulic cylinder supporting a cushion pad and generating a die cushion pressure when a slide of the press machine moves downward, the hydraulic cylinder including a lower chamber in which a cushion pressure is generated; a proportional valve and a hydraulic pump and motor connected in parallel between the lower chamber of the hydraulic cylinder and a low-pressure source; an electric motor connected to a rotating shaft of the hydraulic pump and motor; a die cushion pressure command issuer outputting a die cushion pressure command; a pressure detector detecting a pressure in the lower chamber of the hydraulic cylinder; and a controller configured to control an aperture of the proportional valve and a torque of the electric motor in a manner that the die cushion pressure becomes equal to a pressure corresponding to the die cushion pressure command, based on the die cushion pressure command and the pressure detected by the pressure detector.