At present, the 20-ton Hitachi excavator uses a dual-circuit constant power control hydraulic system with four operation control modes, which can realize electrical control and hydraulic control.
Double pumps are controlled according to the full power variable. It means that the sum of the powers of the two pumps remains constant. This is mainly because when a single pump is executed, the pump can absorb the power of another non-working hydraulic pump to give full play to the power of the diesel engine.
At present, the main hydraulic components are Japanese KAWASAKI (Kawasaki) hydraulic components, and the main components are as follows:
1. Main pump
K3V112DT plunger type series variable double pump with a maximum displacement of 112ml/r. The pump can achieve full electrical control. The computer can control the variables of the main pump in real time according to the load size and control selection. At the same time, it can be converted into Hydraulic control mode.
The original picture of the main pump is as follows:
2. Main operating valve
Using Kawasaki KMX15RA, the maximum flow rate is 270L/min, which can realize boom lifting confluence, stick big and small cavity confluence, stick regeneration circuit, walking straight line, boom lifting priority, swing priority, stick lock, boom lock, and swing throttling And other functions.
2.1 Principle diagram of main valve
2.2 The main valve structure is as follows:
