1. Structure composition of electric drive hydraulic excavator
The structure of electrohydraulic excavator is similar to that of ordinary hydraulic excavator, but the power source is changed from diesel engine to frequency conversion motor. The power source is composed of frequency conversion motor and frequency converter, and the cable or battery supplies power to the motor. The working process is: power supply to the inverter, through the inverter to the inverter motor power supply, used to realize the motor speed control.
2. Hydraulic system principle of electric drive hydraulic excavator
The control circuits of hydraulic excavator are load sensitive system, positive flow control system and negative flow control system. This paper introduces a load sensitive system which is anti flow saturation, or LUDV system.
LUDV system consists of load sensitive pump, load compensation multi-channel valve, shuttle valve and its respective actuator. Its characteristics are that the pressure compensation valve is located at the throttle port of the multi-channel reversing valve. The maximum load pressure detected by the shuttle valve acts on the valve core of all pressure compensation valves, and is balanced with the pressure of the oil inlet of each self pressure compensation valve, At the same time, the maximum load pressure is introduced to the control oil port of load sensitive pump. The outlet pressure of the control pump is always higher than the maximum load pressure. In this way, the pressure difference acting on all the multi-channel valve orifice will be kept constant. Once the flow set by the system is greater than the maximum flow provided by the pump, the pressure difference of each orifice of the multi-channel valve can be maintained constant, The flow rate of each actuator is reduced in the same proportion, so that the proportional relationship of the speed of each hydraulic actuator is not changed.
