Introduction of four categories of hydraulic system of construction machinery       

Today, the construction machinery house Xiaobian to explain the four categories of hydraulic system for construction machinery.

The hydraulic cylinder and gradually realize the standardization and serialization of the varieties, specifications, quality and performance have been greatly improved, especially the new technology using electronic technology, servo technology and other new technology, the quality of the hydraulic system has been greatly improved, which has played an important role in the national economy and military industry.

From different angles, the hydraulic system can be divided into 4 different forms.

(1) the way the cycle of oil, the hydraulic system can be divided into open system and closed system. Open system refers to the hydraulic pump oil absorption from the tank, the oil through a variety of control valves, drive hydraulic actuator, return oil, and then through the reversing valve back to the tank. The system structure is relatively simple, can play the role of heat dissipation and precipitation impurities, but the oil is often contact with the air, so that the air is easy to penetrate into the system, resulting in uneven movement of the mechanism and other consequences. The open system of oil tank, oil pump self-priming performance. In the closed system, the inlet pipe of the hydraulic pump is directly connected with the return pipe of the actuating element, and the working fluid is closed in the pipeline of the system. Its compact structure, less contact with the air, the air is not easy to penetrate into the system, so the transmission is more stable. The speed change and commutation of the working mechanism are realized by adjusting the variable mechanism of the pump or motor, avoiding the hydraulic impact and energy loss in the reversing process of the open system. But closed system is more complex than open system, because there is no oil tank, the heat and filtration conditions of the oil are poor. To compensate for system leaks, usually need to fill the pump and tank of a small flow. As the single pole double acting cylinder large cavity flow range, in the work process will make use of power down, so the implementation of a closed system components for hydraulic motor.

(2) according to the number of hydraulic pumps in the system, it can be divided into single pump system, double pump system and multi pump system.

(3) according to the different forms of hydraulic (hydraulic cylinder) pump, it can be divided into quantitative pump system and variable pump system. The advantages of variable pump is within the scope of the regulation, can make full use of the power of the engine, but its structure and complex manufacturing process, high cost, can be divided into manual variables, as far as possible control variables, servo variable, pressure compensating variable and constant pressure variable, hydraulic variable etc..

(4) according to the supply to the actuator in different ways, can be divided into series system and parallel system. In the series system, the return oil of the last actuator is the oil of the next actuating element, and the pressure is reduced once per actuator. In series system, when the main pump is controlled by the manifold valve, the movement of each actuator can be realized as long as the outlet pressure of the hydraulic pump is enough. But because the pressure of the actuator is superposed, the ability to overcome the external load will decrease with the increase of the number of the actuators.

Modern engineering machinery almost adopts the hydraulic system (hydraulic cylinder), and combined with electronic system, computer control technology, become an important part of modern construction machinery.