DIE CUSHION DEVICE OF PRESS MACHINE.

摘要

An object of the present invention is to provide a die cushion device of a press machine, wherein preliminary acceleration can be applied to a die cushion pad following the descent of a slide at an accurate timing and with high accuracy, and such improvements can be achieved that a difference in pressure between a real pressure in a hydraulic cylinder and a preset target value can be eliminated in the vicinity of a bottom dead center of a slide stroke. Said die cushion device comprises an air pressure cylinder (6) and a hydraulic cylinder (7) having a servo valve (40) for controlling a discharge pressure and fed with pressure oil through suction, wherein the supply of the pressure oil to the hydraulic cylinder (7) at the time of said preliminary acceleration is performed through a pressure oil supply circuit (16) provided with a servo valve (22) being controlled by a main body (14) of a control device, and a control signal from a main body (27) of a pressure control device for controlling the servo valve (40) for controlling the discharge pressure in the hydraulic cylinder (7) is corrected in accordance with a speed of slide descent and a speed of press operation.