Structure and working principle:
The above picture shows the overall structure of wheel loader, which generally consists of frame, power transmission system, walking device, working device, steering braking device, hydraulic system and control system. The power of the engine 1 is transmitted to the gearbox 14 through the hydraulic torque converter 2, and then the gearbox transmits the power to the front and rear axle 10 through the transmission shaft 13 and 16 respectively, driving the wheels to rotate. The pow of that internal combustion engine also drives the hydraulic pump 3 to work through the transfer case. The working device consists of a boom 6, a rocker arm 7, a connecting rod 8, a bucket 9, a boom hydraulic cylinder 12 and a rocker hydraulic cylinder 5. One end of the boom is hinged to the frame, and the other end is equipped with a bucket. The lifting of the boom is driven by the boom hydraulic cylinder, and the overturning of the bucket is realized by the rotary bucket hydraulic cylinder through the rocker arm and connecting rod. The frame 1 1 consists of a front part and a rear part, and the middle part is connected by a hinge pin 4. Through the steering hydraulic cylinder, the front and rear frames can rotate relatively around the hinge pin to realize steering.
Function: The main function is to shovel loose materials in short distance. It is one of the types of construction machinery with the largest production, sales and market demand and the fastest development. We usually see wheel loaders, not crawler loaders. Compared with crawler, it has the advantages of good maneuverability, no damage to the road surface and convenient operation. Therefore, wheel loaders are widely used. The research objects of this paper are all wheel loaders.
As can be seen from the overall structural diagram of the loader, the loader can be divided into power system, mechanical system, hydraulic system and control system. As an organic whole, the performance of loader is not only related to the performance of the mechanical part of the working device, but also to the performance of the hydraulic system and control system. Power system: The power of loader is generally provided by diesel engine, which has the characteristics of reliable operation, hard power characteristic curve and fuel economy, and meets the requirements of harsh working conditions and variable load of loader. Mechanical system: mainly includes walking device, steering mechanism and working device. Hydraulic system: the function of this system is to convert the mechanical energy of the engine into hydraulic energy by using the oil pump, and then transfer it to the oil cylinder, oil motor, etc. And convert it into mechanical energy. Control system: The control system is a system that controls the engine, hydraulic pump, multi-way directional valve and actuator. Hydraulic control drive mechanism is a device that converts tiny power electric energy or mechanical energy into powerful hydraulic energy and mechanical energy in hydraulic control system. It consists of hydraulic power amplifier, hydraulic actuator and load, and is the core of static and dynamic analysis in hydraulic system.
Development status and existing problems of loaders at home and abroad;
At present, foreign multi-functional logistics equipment and related technologies are improving day by day, and are developing in the direction of serialization, large-scale, miniaturization and multi-function. Internationally renowned manufacturers (such as Bobcat, Case, Caterpillar, Komatsu, Li Boer, Volvo, etc.). Widely use microelectronics and information technology, improve computer-aided driving system and information management system, such as electronic monitoring and automatic alarm system, GPS positioning and automatic weight weighing device, to realize accurate loading, loading and operation of materials; Secondly, special noise reduction materials and noise suppression methods are adopted to eliminate or reduce the machine noise when the loader is working; Thirdly, by continuously improving the EFI device, the exhaust emission of diesel engine can be further reduced, and a pollution-free, economical and environmental-friendly power device can be studied; Fourth, optimize the structural design of the working device, such as the single? z？ T-shaped linkage mechanism evolved into eight-bar parallel mechanism, TP linkage mechanism and? ERASLINK？ Mechanism (single arm cast steel structure), and O&; In order to improve the productivity of loaders, Lear linkage specially designed by K company has developed many super-functional systems, such as power electronic control/management system, which can automatically adjust the output power of engines; Engine automatic control system, when the loader is in non-working state, automatically reduce the engine speed, reduce fuel consumption and engine noise; Key information display system, etc.
The leading products in China's loader industry are basically developed on the basis of ZL50 developed by Liugong in the early 1970s, which belongs to the international technical level in the 1960s. In the 1980s, we digested and absorbed advanced technologies such as Caterpillar of the United States and Komatsu of Japan, and gradually developed the second generation loader products in China. Compared with international advanced products, there is a big gap in electromechanical integration, operating comfort and working efficiency of the second generation products in China. The biggest gap is product reliability. Domestic multifunctional loaders have poor reliability (the average time between failures is less than 400 hours), lack of core technology, dependence on imports for major key parts, single product and low product grade. Although the research work of domestic loaders and related technologies started late, it developed rapidly. For example, the sales volume of multifunctional loaders has occupied half of the world loader market, and China has become the largest producer and exporter of multifunctional loaders in the world.
At present, the third generation products have appeared in China loader industry. The reliability of the third generation products has been greatly improved, and the main performance indexes can basically reach the international advanced level. However, there is still a considerable gap between China and foreign countries in terms of reliability, comfort, work efficiency and manufacturing level. The fourth generation of products also appeared on the basis of the third generation. The performance and configuration of the whole machine were further optimized, and technologies such as electric cabinet and wet brake were applied to form proprietary technologies and patented technologies of various enterprises, so that the products were brought to the market with a brand-new look. These will further promote the technical progress of China loader industry.
Development trend of loaders;
Microelectronics technology and information technology will be widely used to further improve the computer-aided driving system, information management system and fault diagnosis system; Adopt single sound absorption material and noise suppression method to eliminate or reduce machine noise; By continuously improving the EFI device, the exhaust emission of diesel engine is further reduced. In addition to the above, there are various working devices such as multifunctional bucket, scarifier, hydraulic hammer and snow blower, which are small in size, high in power, light and flexible, and have better fuel economy, such as increasing the cab size and glass window area, increasing indoor air pressure to prevent dust, improving the position of control system and joystick, improving the comfort of operating environment, reducing the labor intensity of operators and beautifying the appearance. Especially due to the late start of backhoe loaders in China, there is a considerable gap between China and foreign countries in product variety, performance parameters, reliability and after-sales service. Therefore, its development trend is to introduce foreign advanced technology, develop high-quality, multi-functional, multi-variety and multi-specification series products, and improve the market competitiveness of products; Strengthen the production and quality of basic parts, especially improve the quality of hydraulic components, and reduce the cost of products on the premise of meeting the reliability requirements of products; Improve the after-sales service quality of products.
References:
Development status of wheel loader technology abroad in Wang Guobiao.
Song Zhanwei, Wen Bangchun, Development and application of electronic control technology for loaders.
Zhu, the development of wheel loader products in China
Present situation and technical development of wheel loaders.