Pump controller for construction machine

A pump controller for a construction machine, said construction machine including a plurality of variable displacement hydraulic pumps, a plurality of control valves connected in series to center bypasses attached to each of said variable displacement hydraulic pumps and a plurality of actuators to receive and drive a pressure oil whose flow rate and direction are controlled by said control valves, said controller comprising:

• means for generating a control pressure for negatively controlling a discharge from said variable displacement hydraulic pump, said means for generating a control pressure being installed at a terminal part of a center bypass line extending from a discharge port of each of said variable displacement hydraulic pumps and passing through said center bypass, wherein, with regard to a specific one of said actuators, pressure oils discharged from a plurality of said variable displacement hydraulic pumps are combined through a confluent valve;
• recognition means for recognizing an operation of each of said actuators;
• a sensor that converts said control pressure into an electric signal and outputs said electric signal;
• pump characteristic setting means for setting a basic pump discharge characteristic, when said specific actuator does not receive a confluent flow, and setting an extra increment pump discharge characteristic made by continuously increasing a maximum discharge point from a specific point on said basic pump discharge characteristic, when said specific actuator receives said confluent flow;
• pump discharge calculation means for obtaining a pump discharge in accordance with said electric control signal outputted from said sensor and said pump discharge characteristic set by said pump characteristic setting means;
• and
• variable discharge means for converting said pump discharge obtained by said pump discharge calculation means into a pump control signal and outputting said pump control signal to said variable displacement hydraulic pump.

A pump controller for a construction machine, said construction machine including a variable displacement hydraulic pump, a plurality of control valves connected in series to a center bypass attached to said variable displacement hydraulic pump and an actuator to receive and drive a pressure oil whose flow rate and direction are controlled by said control valve, said controller comprising:

• means for generating a control pressure for negatively controlling a discharge from said variable displacement hydraulic pump, said means for generating a control pressure being installed at a terminal part of a center bypass line extending from a discharge port of said variable displacement hydraulic pump and passing through said center bypass;
• recognition means for recognizing an operation of each of said actuators;
• a sensor that converts said control pressure into an electric signal and outputs said electric signal;
• second recognition means for recognizing that a load mounted on said actuator is replaced by a different load;
• pump characteristic setting means for setting a pump discharge characteristic made by continuously increasing or decreasing a maximum discharge from a specific point on a normal pump discharge characteristic to the actuator with said different load mounted thereon, when said load is replaced by said different load;
• pump discharge calculation means for obtaining a pump discharge in accordance with said electric control signal outputted from said sensor and said pump discharge characteristic set by pump characteristic setting means;
• and
• variable discharge means for converting said pump discharge obtained by said pump discharge calculation means into a pump control signal and outputting said pump control signal to said variable displacement hydraulic pump.