1 Power plant
The power unit of single bucket hydraulic excavator mostly adopts vertical multi-cylinder, water-cooled, one-hour power calibration diesel engine.
2 Transmission system
The transmission system of the single bucket hydraulic excavator transmits the output power of the diesel engine to the working device, the slewing device and the traveling mechanism through the hydraulic system.
3 Slewing mechanism
The swivel mechanism makes the working device and the upper turntable swivel left or right for excavation and unloading. The slewing device of the single bucket hydraulic excavator must be able to support the turntable on the frame without tilting and make the slewing light and flexible. For this reason, the single bucket hydraulic excavator is equipped with a slewing support device (supporting) and a slewing transmission device (driving the turntable to rotate), which are collectively referred to as a slewing device.
3.1 Slewing support
The single bucket hydraulic excavator uses a slewing support structure to realize the rotation of the upper platform. According to the structure, the slewing support is divided into two types: column type and rolling bearing type.
3.2 Slewing drive
The transmission type of the slewing device of the full-rotation hydraulic excavator includes direct transmission and indirect transmission.
1) Direct drive. A drive pinion is installed on the output shaft of a low-speed high-torque hydraulic motor to mesh with the rotary gear ring. Excavators generally do not adopt this type of structure.
2) Indirect transmission. An indirect transmission structure in which a high-speed hydraulic motor drives a rotary ring gear through a gear reducer. This transmission type has a compact structure, a larger transmission ratio, and a better force on the gears. The structure of the axial piston hydraulic motor is basically the same as that of the same type of hydraulic oil pump, and many parts can be used in common, which is convenient for manufacturing and maintenance, thereby reducing the cost.
4 Walking mechanism
The walking mechanism supports the overall quality of the excavator and completes the walking task.
The basic structure of the crawler-type walking mechanism of the single-bucket hydraulic excavator is roughly the same as that of other crawler-type mechanisms, but it uses two hydraulic motors to drive one crawler each. Similar to the transmission of a slewing device, a high-speed small torque motor or a low-speed large torque motor can be used. When the two hydraulic motors rotate in the same direction, the excavator will travel in a straight line; if only one hydraulic motor is supplied with oil and the other hydraulic motor is braked, the excavator will steer around the track on the braking side; The hydraulic motor rotates in reverse, and the excavator will turn in place.
All parts of the traveling mechanism are installed on the integral traveling frame. The pressure oil output by the hydraulic pump enters the walking hydraulic motor through the multi-way reversing valve and the central swivel joint. The motor converts the pressure energy into output torque and transmits it to the driving wheel through a gear reducer. Finally, the crawler is wound to realize the excavator walk.
Most single-bucket hydraulic excavators use combined structural crawlers and flat crawler shoes—no obvious crawling. Although the adhesion performance is poor, it is durable and less destructive to the road surface. It is suitable for hard rocky ground operations or frequent shift operations. There is also a three-track spur track shoe, which has a larger grounding area and a shallow depth of the spur cut into the soil, which is suitable for excavator quarrying operations. After the implementation of standardization, it is stipulated that the excavator adopts rolled track shoes with light weight, high strength, simple structure and lower price. The triangular track shoe dedicated to the swamp can reduce the ground pressure and improve the passing capacity of the excavator on soft ground.
The driving wheels of the single bucket hydraulic Hitachi excavator are all made of integral castings, which can be correctly meshed with the track and balanced in transmission. When the excavator is walking, the driving wheel should be located at the rear to make the tension section of the crawler shorter, and reduce the friction, wear and power consumption of the crawler.
Each crawler is equipped with a tensioning device to adjust the tension of the crawler and reduce the vibration, noise, friction, wear and power loss of the crawler. At present, single-bucket hydraulic excavators adopt hydraulic tensioning structure. The hydraulic cylinder is placed inside the buffer spring, reducing the overall size.
5 Working device
There are many types of hydraulic excavator working devices (up to more than 100 kinds). At present, backhoes and breakers are the most used in engineering construction.
Articulated backhoe is the most commonly used structure of single-bucket hydraulic excavators. The main components such as the boom, stick and bucket are hinged to each other (see Figure 2-1). Under the action of the hydraulic cylinder, each component swings around the hinge point. Complete excavation, lifting and unloading operations
