The maximum design working pressure of hydraulic system of excavator is 31.5Mpa. The hydraulic actuators of the boom, stick, bucket, bucket opening and walking device of the excavator are supplied by four main working pumps. Each main working pump controls the hydraulic actuator through a group of proportional multi-channel valves. Among the four groups of proportional multi-channel valves, two groups are sequential single action control, and the other two groups are combined control of parallel and sequential single action. The flow control of the hydraulic actuator is carried out through the combined flow outside the valve, so that the four main working pumps can supply oil to the actuator respectively.
The hydraulic system of excavator adopts positive flow control system. The pilot pressure output by the proportional reducing valve is controlled by the control handle. The proportional reducing valve is supplied by a separate pilot pump. The pilot control pressure controls the opening of the proportional multi-channel valve and the displacement of each main pump at the same time. The flow matching is realized and the energy consumption of the hydraulic system is reduced.
The displacement of the hydraulic pump is proportional to the pilot pressure value, which is a positive flow pump. At the same time, the hydraulic pump adopts constant power control. The constant power value can be realized through external control. Adjusting the constant power value can realize the control of different working conditions. Different constant power values of the hydraulic pump can be set according to different working conditions.
The bucket and the bucket opening device are controlled by two identical hydraulic cylinders respectively. In the hydraulic control system, the bucket hydraulic cylinder can be supplied by three main pumps at most, and the bucket opening hydraulic cylinder can only be supplied by one main pump. In the hydraulic system, the combination control of electro-hydraulic proportional variable pump and proportional multi-channel valve is adopted.
