Die cushion device for press machine

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.