As shown in Figure 2.1, the basic structure of the hydraulic excavator mainly includes: bucket 1, bucket cylinder 2, arm 3, arm cylinder 4, boom 5, boom cylinder 6, cab 7, turntable 8, power Device and counterweight 9 and walking device 10 and so on. The basic actions included in the operation process of the hydraulic excavator are: bucket excavation, bucket and unloading I; stick retracting II; boom lifting and lowering III; turntable turning left and right VIV; whole machine walking V and other auxiliary Sports etc.
For hydraulic excavators, the above actions are all driven by the hydraulic system. Because the working objects and working environment of the hydraulic excavator are variable, in order to adapt to this situation and improve the engine power utilization rate and excavator working efficiency, the host must have the following three functions:
(1) The automatic adaptability of action speed and external load. When the external load is small, you want to increase the output flow of the variable pump and increase the movement speed of the actuator; when the external load is large, you want to reduce the output flow of the variable pump and reduce the movement speed of the actuator.
(2) Compound action ability. In order to improve the operating efficiency and engine power utilization rate of the excavator, and to meet the needs of various operating conditions, the excavator often requires two or more actions to be performed simultaneously during the operation process, that is, it is required to be able to achieve a compound action.
(3) Combined oil supply capacity. At present, most hydraulic excavators are multi-pump and multi-circuit systems. When a single actuator moves, it is required to be able to merge hydraulic oil of different circuits onto a single actuator to merge and supply oil to improve operating efficiency.
Figure 2.2 is the composition and action composition of a working cycle of a hydraulic excavator, which includes:
(1) Excavation: The excavation operation is mainly completed by the bucket hydraulic cylinder or the arm hydraulic cylinder. Therefore, the excavation operation is mainly a composite action of the bucket and the arm, or is equipped with a boom action.
(2) Full bucket lifting and turning: After the excavation is completed, the boom is raised and the turntable is turned to the discharge place. This action is mainly completed by the boom hydraulic cylinder and the rotary hydraulic motor. Therefore, the full bucket lifting and turning action is mainly to move Compound movement of arm and turntable.
(3) Unloading: After the turntable turns to the discharge point, brake, adjust the unloading position with the stick, and unload the bucket. This action is completed by the stick hydraulic cylinder and the bucket hydraulic cylinder, or equipped with a boom hydraulic cylinder. Therefore, the unloading action is mainly a compound action of the arm and bucket, or a boom action.
(4) Return of empty bucket: After the unloading is completed, the turntable is reversed and the empty bucket is placed at a new excavation point. This action is mainly completed by the rotary hydraulic motor, boom hydraulic cylinder and arm hydraulic cylinder. The return action of the empty bucket is mainly a compound action of the turntable, the boom and the stick.
