Structure and working principle of excavator

Hydraulic excavator is mainly composed of engine, hydraulic system, working device, walking device and electrical control. The hydraulic system consists of hydraulic pump, control valve, hydraulic cylinder, hydraulic motor, pipeline, oil tank and so on. Electrical control system includes monitoring panel, engine control system, pump control system, various sensors, solenoid valve, etc. Hydraulic excavator generally consists of working device, rotary device and walking device (figure 1). According to its structure and use can be divided into: crawler type, wheel type, walking type, full hydraulic pressure, half hydraulic pressure, full rotation, non-full rotation, universal type, special type, articulated type, telescopic arm type and other types. The working device is a device to complete the excavation task directly. It consists of three parts, such as moving arm, bucket, bucket and so on. The lifting and falling of moving arm, expansion and contraction of bucket bar and rotation of bucket are controlled by reciprocating double-acting hydraulic cylinder. In order to meet the needs of different construction operations, hydraulic excavators can be equipped with a variety of working devices, such as excavation, lifting, loading, leveling, clamps, earth pushing, hammer and so on (figure 2). The rotary and walking device is the body of hydraulic excavator, and the upper part of the turntable is equipped with power device and drive system. The engine is the power source of the hydraulic excavator, most of which USES diesel to be in the convenient site, or the electric motor can be used. The hydraulic transmission system transfers the power of the engine to the hydraulic motor, hydraulic cylinder and other executive components through the hydraulic pump to push the working device to complete various operations. Take the pv-200 hydraulic excavator, which is often used in the construction site, as an example. The machine USES an improved open central load sensing system (OLSS). The system reduces the power output of the engine, thereby reducing fuel consumption, by controlling the swash plate Angle (output flow) of the swash plate variable plunger pump, and is an energy efficient system (see figure 3). The characteristics of this hydraulic system are: constant torque control, can maintain the hydraulic pump drive torque constant, load break control, can reduce the unloading loss of operating time; Oil volume control can reduce the output flow of hydraulic pump when neutral and fine tuning control, reduce power loss.