The hydraulic system of hydraulic excavator is composed of power components, executive components, control components and auxiliary devices connected by oil pipes in a certain way.
Excavators generally work in construction sites, so the working environment is poor, which requires the hydraulic system and actuator of excavators to have sufficient strength and very good sealing performance. Due to the frequent action of the excavator, the hydraulic components and pipelines should be able to withstand frequent hydraulic impact to ensure that the excavator can work safely and stably for a long time.
In order to limit the boom, stick and bucket to drop rapidly due to their own weight, one-way throttle valves are set on their circuits, and the whole machine is driven by the travel motor. The left and right motors belong to two independent oil circuits respectively. If the two directional valves are operated at the same time to make them in the left and right positions, the left and right motors will rotate forward or reverse, and the speed is the same. Therefore, the excavator can travel in a straight line, which is difficult to do if a single pump system is used. A hydraulic two speed valve is set in the left and right traveling motors to obtain the speed limit valve on the oil return circuit of the two speed traveling system, which is used to automatically control the traveling speed when the excavator goes downhill to prevent overspeed and landslide. When driving or digging on a flat road, due to the high oil pressure at the outlet of the hydraulic pump, the high-pressure oil will make the speed limiting valve in the left position through the shuttle valve, so as to cancel the return oil throttling. During the digging operation, the boom cylinder and stick cylinder often need to act quickly to improve the production efficiency. To this end, a confluence valve is added to the system. When the control confluence is in the left position, the pressure oil output by the pump enters the multi-channel valve group through the left position of the confluence valve and supplies oil to the boom cylinder and stick cylinder together with another pump to speed up the action speed of boom and stick. A safety valve is set on the oil inlet of the two groups of multi-way valves to limit the maximum working pressure of the system. Overload valves are set on the branch oil circuits of each hydraulic cylinder and hydraulic motor to absorb the impact energy of the working device.
