AIR PRESSURE ADJUSTING METHOD FOR DIE CUSHION AND THE LIKE

PURPOSE:To eliminate the hysteresis error of a drop pressure by controlling the air release with the controlling current which makes a set pressure and by adjusting the pressure with the controlling current after the re-release, in the pressure dropping of the mechanism which controls the pressure of the part to be pressure controlled. CONSTITUTION:The pressure of a pressure air source 5 is made the set secondary pressure by operating the secondary pressure pilot port P of the pilot pressure reducing valve 6 with relief by operating the solenoid 11 of the electropneumatic ratio valve 10 of an electropneumatic pressure control device 12 with the actuation of the microprocessor 21 by a memory device 22 by turning a switch 24 on, in case of dropping the pressure of a balance cylinder 1. The cylinder 1 pressure is simultaneously made the set pressure by opening the solenoid operation 15 changing valve 14. After the fixed time by a timer 23, the control current is cut off, the air is released for short time once, the control current is passed again and the pressure is adjusted. The air pressure hysteresis error at the pressure dropping time is eliminated and the cylinder 1 pressure is correctly made the prescribed pressure.