The excavator basically adopts hydraulic transmission. According to the transmission requirements of various mechanisms and devices of the excavator, various hydraulic components (including hydraulic pumps, hydraulic motors, hydraulic valves, hydraulic cylinders, etc.) are organically connected by pipelines in a certain way The combination is called the hydraulic system of the excavator. The function of the hydraulic system is to use the hydraulic oil as the medium of the mechanical energy of the engine, use the hydraulic pump to convert the mechanical energy of the engine into the hydraulic energy of the hydraulic system, and transmit it, and finally return to the mechanical energy through the hydraulic cylinder or hydraulic motor to achieve various tasks action. According to the different functions, the hydraulic system of the excavator can be divided into three basic parts: the hydraulic system of the walking device, the hydraulic system of the slewing device and the hydraulic system of the working device. The walking device is the supporting part of the whole excavator. It is used to bear the weight of the whole machine and the reaction force of the excavation of the working device, so that the whole machine is stably supported on the ground. At the same time, it also needs to complete the walking task, most of which are wheeled and crawler. , Driven by a walking hydraulic motor. The function of the slewing device is to complete the left and right rotation of the vehicle during excavation and unloading. It is driven by a rotary hydraulic motor. The working device is mainly composed of bucket, bucket cylinder, stick, stick cylinder, boom and boom cylinder. It includes three hydraulic systems: bucket, stick and boom [1].
The hydraulic excavator has multiple actuators (buckets, sticks, booms, slewing, walking, etc.), multiple degrees of freedom, and a large number of hydraulic actuators, requiring more complex movements to be achieved; and it needs to be frequently started during the operation process , Braking and reversing, the external load changes greatly, the impact and vibration are frequent, and the working environment is harsh. Therefore, high requirements are placed on the hydraulic system of the excavator, mainly including the following aspects:
(1) The hydraulic excavator requires high control performance, and requires fine movement when performing fine operations. When high productivity is required, it requires fast action, and the speed range is wide, and the working objects and working conditions of the excavator are variable. Therefore, The speed control performance of each actuator is better.
(2) When hydraulic excavator is working, each hydraulic actuator needs to be able to operate independently or to cooperate with each other to perform a compound action, and it is required that the bucket, stick, boom, slewing and walking can be compounded and compounded. The action form requires complex and diverse. The compound maneuvering performance is required to be good, and it is necessary to be able to reasonably distribute the flow and power of each hydraulic actuator participating in the compound action.
(3) The hydraulic excavator has high power, long working time, large energy consumption, and high requirements on the efficiency of the hydraulic system, thereby reducing energy consumption and emissions. At the same time, the system must have good heat dissipation performance, and the hydraulic oil temperature cannot be too high. The loss of hydraulic components and pipelines should be reduced as much as possible, so the hydraulic system of the hydraulic excavator must fully consider energy saving.
(4) Improve engine power utilization as much as possible, improve economy and reduce emissions. When the external load changes, it is required that the hydraulic system and the engine have a good power match.
(5) In order to improve work efficiency and reduce the labor intensity of the driver, flexible, simple and labor-saving operation is required.
(6) The mechanical work is required to be safe and reliable. The hydraulic components should have good overload protection and buffering devices. The walking mechanism and the slewing mechanism must have reliable braking and speed limit. It is necessary to prevent the boom and boom from dropping rapidly due to their own weight. The whole machine is speeding downhill.
