At first, the excavator was manual, and it has been more than 130 years from its invention to 2013. During the period, it has experienced the gradual development process of automatic hydraulic excavator from steam driven bucket rotary excavator to electric driven and internal combustion engine driven rotary excavator, and automatic hydraulic excavator applying electromechanical hydraulic integration technology. The first hydraulic excavator was successfully invented by the Birkland factory in France. Due to the application of hydraulic technology, in the 1940s, there were hydraulic backhoe hanging excavators on tractors. In 1951, the first fully hydraulic backhoe excavator was launched by the Poclain (Bokland) factory in France, thus creating a new space in the field of excavator technology development. In the early and mid-1950s, towed full rotary hydraulic excavator and crawler full hydraulic excavator were developed successively. The initial trial production of hydraulic excavator is the hydraulic technology of aircraft and machine tools, the lack of hydraulic components suitable for various working conditions of excavator, the manufacturing quality is not stable, and the accessories are not complete. Since the 1960s, hydraulic excavator has entered the stage of promotion and vigorous development, excavator manufacturers and varieties in various countries have increased rapidly, and the output has soared. From 1968 to 1970, the output of hydraulic excavator accounted for 83% of the total output of excavator, close to 100% [2].
The first generation of excavator: the emergence of electric motor and internal combustion engine, so that the excavator has an advanced and appropriate electric devices, so a variety of excavator products have been born. In 1899, the first electric excavator appeared. After World War I, diesel engines were also used in excavators, and the mechanical excavator driven by diesel engines (or electric motor) was the first generation of excavators.
The second generation of excavator: with the extensive use of hydraulic technology, the excavator has a more scientific and applicable transmission device, hydraulic transmission instead of mechanical transmission is a big leap in excavator technology. In 1950, the first hydraulic excavator was born. Mechanical transmission hydraulic pressure is the second generation of excavator.
The third generation of excavator: electronic technology, especially computer technology, so that the excavator has an automatic control system, but also make the excavator to high performance, automation and intelligent direction development. The germination of mechatronics took place around 1965, and the mechatronics technology for mass-produced hydraulic excavators was used around 1985, when the main purpose was to save energy. Electronic excavator is the symbol of the third generation of excavator.
Excavator industry manufacturers can be roughly divided into four categories. More than 70% of domestic excavators are occupied by foreign brands, and domestic brands are still mainly small digging and medium digging, but the share of domestic excavators is gradually increasing, with a year-on-year increase of 3.6% in 2012.
Since the late 20th century, the international production of excavators has been developed to the direction of large-scale, miniaturization, multi-function, specialization and automation.
1. Develop multi-variety, multi-functional, high-quality and high-efficiency excavators. In order to meet the needs of municipal construction and farmland construction, micro-excavators with a bucket capacity below 0.25m³ have been developed abroad, and the minimum bucket capacity is only 0.01m³. In addition, the largest number of small excavators tend to a machine, equipped with a variety of working device —— in addition to the shovel, shovel, also equipped with lifting, grab, flat bucket, loading bucket, rake teeth, broken cone, twist, drilling, electromagnetic suction cup, vibrator, push board, impact shovel, fork, aerial frame, hinge plate and shovel, etc., to meet the needs of various construction. At the same time, the development of special use of special excavators, such as low specific pressure, low noise, underwater special and amphibious excavators.
2. Rapid development of full hydraulic excavator, continuous improvement and innovation of control mode, so that excavator from simple lever operation to hydraulic control, pressure control, hydraulic servo control and electrical control, radio remote control, electronic computer integrated program control. In dangerous areas or underwater operations, the combination of electronic computer control receiver and laser guidance, to realize the complete automation of excavator operation. All this, the full hydraulic pressure of the excavator has laid the foundation and created a good premise.
3. Attach importance to the adoption of new technologies, new processes and new structures, and accelerate the development speed of standardization, serialization and generalization. For example, the excavator produced by Atlas is equipped with new engine speed regulating device to suit the operating speed, and the new C series LC-5800 hydraulic excavator is installed with automatic control hydraulic system, which can automatically adjust the flow rate and avoid the waste of driving power. The CAPS (Computer-aided Power System) is also installed, Improve the operating power of the excavator, Better to give full play to the function of the hydraulic system; Five new models of excavators produced by Sumitomo Japan are equipped with a computer-assisted power control system connected to the hydraulic circuit, Using the fine-control mode selection system, Reduce the fuel, engine power, and hydraulic power consumption, And extend the service life of the parts; The oil pump regulating system of excavator produced by Ogakai (O & K) has confluence characteristics, Make the oil pump have the maximum working efficiency; Using the intelligent control system on the new 904.905.907.909 type hydraulic excavator, Even inexperienced drivers can perform complex operations; Liebherr, Germany developed the ECO (Electronic Control Operations), The operation performance of the excavator can be adjusted according to the operation requirements, The effect of high efficiency and low fuel consumption has been achieved; In the new B system excavator, using the latest 3114T type diesel engine, torque load sensing pressure system, power mode selector, etc., Further improves the operation efficiency and stability of the excavator. Doosan construction machinery company in DH 280 excavator adopted EPOS —— electronic power optimization system, according to the change of the engine load, automatically adjust the power absorbed by the hydraulic pump, make the engine speed always keep near the rated speed, namely the engine always with full power operation, both make full use of the engine power, improve the efficiency of the excavator, and prevent the engine due to overload.
4. Update the design theory to improve the reliability and extend the service life. America, Britain, Japan and other countries using limited life design theory, to replace the traditional infinite life design theory and method, and the fatigue damage accumulation theory, fracture mechanics, finite element method, optimization design, computer control of electrohydraulic servo fatigue test technology, fatigue strength analysis method and other advanced technology applied to the strength of hydraulic excavator research, promote the high quality product efficiency and competitiveness. The United States put forward the dynamic design analysis method of assessing dynamic strength, and established the theory of predicting product failure and update. Japan has developed the strength evaluation procedure of hydraulic excavator components and developed the reliability information processing system. Under the guidance of the above basic theory, with the help of a large number of tests, the research cycle of new products is shortened, the upgrading process of hydraulic excavator is accelerated, and its reliability and durability are improved. For example, the operation rate of the hydraulic excavator reaches 85%~95%, and the service life is more than 10,000 hours.
5. Strengthen labor protection for drivers and improve their working conditions. Hydraulic excavator adopts cab with falling protection structure and tipping protection structure, instadjustable flexible seat, and reduces noise interference with sound insulation measures.
6. Further improve the hydraulic system. The hydraulic system of medium and small hydraulic excavator has an obvious trend to the variable system. Because the variable system in the process of the oil pump, the pressure is reduced by increasing the flow, so that the power of the hydraulic pump remains constant, that is, the hydraulic excavator equipped with the variable pump can often make full use of the maximum power of the oil pump. When the external resistance increases, reduce the flow (reduced speed) and the excavation force is multiplied; use three loop hydraulic system. To produce three independent work movements. To achieve the power matching with the rotary mechanism. The third pump is connected to the other working movements to become the second independent fast movement of the open loop. In addition, hydraulic technology is widely used in excavators, which creates conditions for the application and promotion of electronic technology and automatic control technology in excavators.
7. Rapidly expand the application of electronic and automation technology in excavators. In the 1970s, in order to save energy consumption and reduce environmental pollution, make the operation of excavator light and safe, reduce the noise of excavator, improve the working conditions of drivers, electronic and automatic control technology was gradually applied in the excavation. With the improvement of the excavator work efficiency, energy saving and environmental protection, light operation, safety and comfortable, reliable and durable and other aspects of the performance requirements, has promoted the application of mechanical and electrical liquid integration in the excavator, and make its various performance has a qualitative leap. In the 1980s, the microelectronics technology as the core of high and new technology, especially the microcomputer, microprocessor, sensor and detection instrument application on excavator, promote the electronic control technology on excavator application and promotion, and has become an important symbol of excavator modernization, namely advanced mining with engine automatic idle and throttle control system, power optimization system, working mode control system, monitoring system and other electronic control system.
8. Pay more attention to environmental protection, CAT, Komatsu and other manufacturers have launched excavators to meet the requirements of the three emissions.
