Excavator is an earth moving machine that uses a bucket to excavate materials that are higher or lower than the bearing surface, and loads them into a transport vehicle or discharges them to a stockyard. There are many types of hydraulic systems for excavators, which can be classified according to different aspects. According to the circulation form of oil, it can be divided into open system and closed system. Closed system refers to that the oil inlet pipe of the hydraulic pump is directly connected with the oil return pipe of the actuator, and the working liquid is closed and circulated in the pipeline of the system. This article will introduce the advantages and disadvantages of the closed system for reference only.
1. Advantages
1) Compact structure and small oil tank.
2) There are few opportunities for oil and air to contact, air is not easy to penetrate into the system, and the transmission is stable.
3) High speed pump can be used, so the pump volume can be relatively reduced.
4) There is no control valve, and the flow and direction are determined by the pump.
5) There is no brake valve.
6) The speed change and reversing of the working mechanism are realized by adjusting the variable mechanism of the pump or motor, which avoids the hydraulic shock and energy loss in the reversing process of the open system.
2. Disadvantages
1) Compared with the open system, the system is more complex. Due to the lack of oil tank, the cooling and filtering conditions of the oil are poor.
2) In order to compensate for the leakage in the system, a small flow make-up oil pump and oil tank are usually required.
3) Only as many actions as the number of oil pumps installed can be realized at the same time.
4) The idle stroke speed can only be increased by using a large displacement oil pump or variable displacement motor.
