Figure 2- 1 1 Structure of Excavator
(1) engine
The engine is generally a four-stroke, water-cooled (or air-cooled), multi-cylinder and direct injection diesel engine. A few excavators use electronically controlled diesel engines.
(2) Transmission system
There are three kinds of transmission pumps: mechanical transmission, semi-hydraulic transmission and full hydraulic transmission, among which mechanical transmission and semi-hydraulic transmission are widely used.
(3) Drive system
The traveling system of hydraulic excavator is the supporting part of the whole machine, which bears all the mass of the machine and the reaction force of the working device, and enables the excavator to travel in a short distance. According to different structures, the drive system can be divided into crawler type and tire type.
① Crawler drive system. It consists of crawler, roller, sprocket, driving wheel, guide wheel, tensioner, walking frame, oil motor, reducer, etc.
The traveling system of hydraulic excavator is driven by hydraulic pressure. The driving device mainly includes hydraulic motor, reducer and driving wheel, and each crawler has its own hydraulic motor and reducer. Because the two hydraulic motors can work independently, the left and right tracks of the machine can move forward or backward synchronously, braking one track can realize steering, and driving two tracks in the opposite direction can realize in-situ steering. The operation is very simple, convenient and flexible.
② Tire drive system. It usually consists of a frame, a steering front axle, a rear axle, a walking mechanism and legs.
The rear axle is rigidly and fixedly connected with the frame through bolts. The front axle is hinged with the frame through the suspension balancing device. The function of the suspension balancer is to ensure that the four wheels fully contact the ground by using the swing of the support plate and the floating of the two suspension cylinders when the excavator is driving, so as to reduce uneven load, swing, road impact and fuselage deformation and improve the off-road performance of the excavator. When the excavator is working, the two suspension cylinders are locked to ensure the stability of the whole machine during excavation.
(4) Steering system
The steering system of a tire excavator usually adopts a full hydraulic steering system with front wheel deflection, which is mainly composed of an oil tank (matched with the hydraulic system of the working device), a steering oil pump, a steering gear, an oil filter, a flow control valve, a steering cylinder, an oil pipe and a steering wheel.
The steering system of crawler excavator is relatively simple, which is realized by cutting off the power of driving sprocket. Its steering device is a steering clutch with wet, multi-leaf spring compression, hydraulic separation and manual hydraulic operation mode.
(5) Brake system
The brake of the foot brake device is a cam-opening shoe brake. The brake actuator is pneumatic, which is mainly composed of air compressor, gas control valve, foot brake valve, gas storage tank, two-way check valve, quick release valve, manual pneumatic switch, brake cylinder and barometer.
The brake of the hand brake device is a cam-opening shoe brake, and the transmission mechanism is mechanical. The brake bottom plate is fixed on the upper transmission box cover with screws; The brake drum is fixed on the receiving plate with bolts, and the receiving plate is connected with the driven shaft of the upper transmission box through splines.
When the excavator is working, the hand brake must be released, otherwise it will damage the hand brake or rotate the hydraulic motor.
(6) Working device
Working device is one of the main components of hydraulic excavator. Due to the different nature of work, there are many kinds of working devices, such as backhoe, front shovel, loading and lifting, and a device can have many forms.
(7) Hydraulic system
The main actions of the hydraulic excavator are machine walking, turntable rotation, boom lifting, arm retraction and bucket rotation. According to the above work requirements, the combination of all hydraulic components organically connected by pipelines is called the hydraulic system of hydraulic excavator. The function of the hydraulic system is to transform the mechanical energy of the engine into hydraulic energy by using the oil pump as the medium and transmit it to the oil cylinder, oil motor and so on. , and then converted into mechanical energy, and then transmitted to various execution machines to realize various movements. The hydraulic system of hydraulic excavator usually includes quantitative system, sub-power variable system and total power variable system. According to China's regulations, if the weight of a single bucket hydraulic excavator is less than 8t, the quantitative system should be adopted. If the weight of the machine exceeds 32t, a variable system should be adopted; For machines weighing 8 ~ 32t, both quantitative and variable systems can be used.
Full-power variable system is a hydraulic system widely used in hydraulic excavators at present, and double-pump constant power variable is usually selected. Different types of hydraulic pumps adopt different constant power regulating mechanisms.
The hydraulic system is mainly composed of oil circuit system, pilot control oil circuit system and control system.
(8) Electrical system
The electrical system of hydraulic excavator includes starting circuit, power generation circuit, lighting, instrument, sensor, pressure switch, control circuit composed of solenoid valve and auxiliary circuits (such as air conditioner, radio, etc.). Starting motors are divided into 12V and 24V according to different hosts, and the starting power is divided into 3kW, 3.7kW and 4.8kW.
The power generation circuit mainly includes alternator, voltage regulator, charging indicator light and start switch.
In order to ensure safety, high efficiency, energy saving and normal operation, various signal devices, such as oil temperature alarm, charging indicator light, oil pressure alarm, turn signal light, etc. Installed in the electrical system of excavator to warn the operator. In order to make the operator know the operation of the machine at any time, various instruments are installed in the cab, such as oil pressure gauge, oil temperature gauge, hydraulic oil thermometer and water temperature gauge. Modern imported excavators all adopt advanced electric control devices, which is convenient for maintenance personnel to judge the fault position and repair it in time when the excavator fails.