The Hitachi excavator system is controlled by two microcomputers, namely: Engine Controller (EC) and Pump Valve Controller (PVC).
The engine controller and pump valve controller receive signals from sensors and switches. Two microcomputers analyze the received signal and send the control signal to the actuator. For example: the operator presses the P mode (power mode) switch, an electrical signal is transmitted from the P mode switch to the EC. The EC logic module sends a control signal to the EC motor to increase the engine speed. At the same time, the EC also Send a signal to PVC, PVC analyzes this signal, and sends a control signal to the pump displacement solenoid valve on the main hydraulic pump to increase the flow of the hydraulic pump.
EC and PVC regulate engine speed, hydraulic pump flow and variable pressure compensation valve. EC and PVC are connected through a circuit and exchange signals with each other to improve control performance and efficiency. During the operation, when the flow demand of the hydraulic circuit is less than the flow of the hydraulic pump, PVC limits the flow of the hydraulic pump.
PVC receives signals such as engine speed, hydraulic pump pressure, displacement angle, differential pressure and pilot pressure. On the premise of meeting work needs, PVC always takes the minimum flow rate of the hydraulic pump as a priority. After analyzing all these signals, PVC sends a control signal to the pump regulator (pump displacement solenoid valve) to adjust the flow of the hydraulic pump, so that the system has the best performance and the efficiency is improved.
