Cushion load control device and press machine having cushion load control device

Abstract

A cushion load control device for a press machine includes a hydraulic cylinder 2 forming a die cushion, a hydraulic control valve 4 connected to the hydraulic cylinder 2 , a hydraulic source 6 connected to the hydraulic cylinder 2 via the hydraulic control valve 4 , an opening degree controlling part 11 for outputting a control signal for controlling an opening degree of the hydraulic control valve 4 on the basis of the set pressure value of the hydraulic cylinder, a speed detection unit 15 for detecting the lowering speed of the die cushion, and a signal correction part 18 for correcting the value of the control signal in accordance with the set pressure value and the lowering speed value detected by the speed detection unit 15.

1 . A cushion load control device for a press machine for controlling a press load acting on a die cushion disposed below a slide capable of performing an up-and-down motion, the cushion load control device comprising:
 a hydraulic cylinder which constitutes a die cushion;   a hydraulic control valve configured to be connected to the hydraulic cylinder;   a hydraulic source configured to be connected to the hydraulic cylinder via the hydraulic control valve;   an opening degree controlling part configured to output a control signal for controlling an opening degree of the hydraulic control valve on the basis of a set pressure value of the hydraulic cylinder;   a speed detection unit configured to detect a lowering speed of the die cushion; and   a signal correction part configured to correct a value of the control signal in accordance with the set pressure value and a lowering speed value detected by the speed detection unit,   wherein the opening degree of the hydraulic control valve is controlled on the basis of the control signal corrected by the signal correction part.   
   
   
       2 . The cushion load control device according to  claim 1 , wherein the signal correction part corrects the value of the control signal in such a manner that the opening degree of the hydraulic control valve is reduced as the set pressure value is larger. 
   
   
       3 . The cushion load control device according to  claim 1 , wherein the signal correction part corrects the value of the control signal in such a manner that the opening degree of the hydraulic control valve is reduced as the lowering speed of the die cushion becomes slower. 
   
   
       4 . A press machine comprising:
 a motor;   a converting mechanism including a rotation element driven by the motor to perform rotating motion and configured to covert the rotating motion into reciprocating motion;   a slide configured to be connected to the converting mechanism to perform reciprocating motion; and   a cushion load control device which controls a press load acting on a die cushion disposed below the slide,   wherein the cushion load control device comprises a hydraulic cylinder which constitutes a die cushion; a hydraulic control valve configured to be connected to the hydraulic cylinder; a hydraulic source which is connected to the hydraulic cylinder via the hydraulic control valve; an opening degree controlling part configured to output a control signal for controlling an opening degree of the hydraulic control valve on the basis of a set pressure value of the hydraulic cylinder; a speed detection unit configured to detect a lowering speed of the die cushion; and a signal correction part configured to correct a value of the control signal in accordance with the set pressure value and a lowering speed value detected by the speed detection unit, and   wherein the opening degree of the hydraulic control valve is controlled on the basis of the control signal corrected by the signal correction part.   
   
   
       5 . A cushion load control device for a press machine for controlling a press load acting on a die cushion disposed below a slide capable of performing an up-and-down motion, the cushion load control device comprising:
 a servo motor;   a power transmission unit configured to convert rotating motion of the servo motor into an up-and-down motion to thereby move up and down the die cushion;   a position control part configured to output a control signal for controlling height of the die cushion on the basis of a set load value of the die cushion;   a speed detection unit configured to detect a lowering speed of the die cushion; and   a signal correction part configured to correct a value of the control signal in accordance with the set load value and a lowering speed value detected by the speed detection unit,   wherein the height of the die cushion is controlled on the basis of the control signal corrected by the signal correction part.   
   
   
       6 . The cushion load control device according to  claim 2 , wherein the signal correction part corrects the value of the control signal in such a manner that the opening degree of the hydraulic control valve is reduced as the lowering speed of the die cushion becomes slower.