The basic structure of hydraulic excavator mainly includes: bucket 1, bucket cylinder 2, stick 3, stick cylinder 4, boom 5, boom cylinder 6, cab 7, turntable 8, power unit and counterweight 9, walking device 10, etc. The basic actions included in the operation process of hydraulic excavator are: bucket excavation, bucket retraction and unloading I; Stick retraction and retraction II; Boom lifting and lowering III; Left and right rotation of turntable V Ⅳ; Traveling V and other auxiliary movements of the whole machine.
For hydraulic excavators, the above actions are driven by the hydraulic system. Due to the variable working objects and working environment of hydraulic excavator, in order to adapt to this situation and improve engine power utilization and excavator operation efficiency, the host must have the following three functions:
(1) Automatic adaptability of action speed and external load. When the external load is small, it is hoped to increase the output flow of the variable displacement pump and improve the movement speed of the actuator; When the external load is large, it is desirable to reduce the output flow of the variable displacement pump and reduce the movement speed of the actuator.
(2) Compound action ability. In order to improve the working efficiency and engine power utilization of the excavator, and meet the needs of various working conditions, the excavator often requires two or more actions to be carried out at the same time, that is, it is required to realize compound actions.
(3) Combined oil supply capacity. At present, most hydraulic excavators are multi pump and multi circuit systems. When a single actuator acts, it is required to combine the hydraulic oil of different circuits to a single actuator to supply oil and improve operation efficiency.
The composition and action combination of one operation cycle of hydraulic excavator include:
(1) Excavation: the excavation action is mainly completed by the bucket hydraulic cylinder or stick hydraulic cylinder. Therefore, the excavation action is mainly the composite action of bucket and stick, or combined with boom action.
(2) Full bucket lifting and slewing: after excavation, the boom is lifted and the turntable turns to the unloading place. This action is mainly completed by the boom hydraulic cylinder and slewing hydraulic motor. Therefore, the full bucket lifting and slewing action is mainly the composite action of boom and turntable.
(3) Unloading: after the turntable turns to the unloading point, brake, adjust the unloading position with the stick, and unload the bucket. This action is completed by the stick hydraulic cylinder and bucket hydraulic cylinder, or equipped with boom hydraulic cylinder. Therefore, the unloading action is mainly the composite action of the stick and bucket, or equipped with boom action.
(4) Empty bucket return: after unloading, the turntable reverses and the empty bucket is placed at the new excavation point. This action is mainly completed by the swing hydraulic motor, boom hydraulic cylinder and stick hydraulic cylinder. Therefore, the empty bucket return action is mainly the compound action of turntable, boom and stick.
