Excavator power system

The hydraulic system where the output flow of the main pump is a fixed value is a quantitative hydraulic system; On the contrary, the flow of the main pump can be changed by adjusting the system is called a variable system. In the quantitative system, each actuator works according to the fixed flow provided by the oil pump without overflow, and the power of the oil pump is determined according to the fixed flow and the maximum working pressure. In the variable system, the most common is the double pump double circuit constant power variable system, there are sub-power variable and full power variable. The variable power regulation system is to install a constant power variable pump and a constant power regulator respectively in each circuit of the system, and the power of the engine is evenly distributed to each oil pump; The full power regulation system has a constant power regulator that controls the flow changes of all the pumps in the system at the same time, so as to achieve synchronous variables. 

The oil return of the actuator in the open system flows directly back to the tank, which is characterized by a simple system and good heat dissipation effect. However, the tank capacity is large, the low-pressure oil circuit has more contact opportunities with the air, and the air is easy to penetrate the pipeline and cause vibration. The operation of single-bucket hydraulic excavators is mainly cylinder work, and the difference between large and small cylinders is large, the work is frequent, and the heat is large, so the vast majority of single-bucket hydraulic excavators use open system; The oil return circuit of the actuator in the closed circuit is not directly back to the tank, which is characterized by compact structure, small tank volume, a certain pressure in the inlet and return oil circuit, and air is not easy to enter the pipeline, and the operation is relatively stable to avoid the impact of reversing. However, the system is more complex and the heat dissipation conditions are poor.

 In the local system such as the rotary device of the single-bucket hydraulic excavator, a closed circuit hydraulic system is used. In order to supplement the oil leakage caused by the positive and negative rotation of the hydraulic motor, a refill pump is often provided in the closed system.