Control system for load-sensing hydraulic drive circuit

A control system for a load-sensing hydraulic drive circuit comprising:

• at least one hydraulic pump;
• a plurality of hydraulic actuators driven with hydraulic fluid delivered from said hydraulic pump;
• and a pressure compensated flow control valve connected between said pump and each of said actuators, for controlling a flow rate of the fluid supplied to each said actuator in response to an operation signal from control means, wherein said control system comprises:
• first detection means for detecting a differential pressure between the delivery pressure of said pump and the maximum load pressure among said plurality of hydraulic actuators;
• second detection means for detecting the delivery pressure of said pump;
• first means for calculating, based on a differential pressure signal from said first detection means, a differential pressure target delivery amount Q.DELTA.p of said pump to hold said differential pressure constant;
• second means for calculating an input limiting target delivery amount QT of said pump based on at least a pressure signal from said second detection means and an input limiting function preset for said pump;
• third means for selecting one of said differential pressure target delivery amount Q.DELTA.p and said input limiting target delivery amount QT as a delivery amount target value Qo for said pump, and then controlling the delivery amount of said pump such that the delivery amount does not exceed above said input limiting target delivery amount QT;
• and
• fourth means for calculating a compensation value Qns to limit a total consumable flow rate for said actuator based on at least said input limiting target delivery amount QT and said differential pressure target delivery amount Q.DELTA.p when said input limiting target delivery amount QT is selected by said third means, and then controlling said pressure compensated flow control valve based on said compensation value Qns.