Flexible design of flexible boom mechanism of the

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Flexible design of loader flexible boom mechanism

loader plays a great role in engineering construction because of its efficient and flexible performance. Especially in large-scale water conservancy projects, mines, coal mines and various civil engineering projects, the utilization rate is getting higher and higher. But at the same time, we should also note that among all kinds of construction machinery, loaders not only have a high failure rate, but also have a short service life. This situation not only causes huge economic losses to the majority of users, but also makes the maintenance cost of enterprises remain high

using a known weight (counterweight) to adjust is called "f calibration". Through in-depth analysis of the information fed back by the market and users, as well as research on the structural principle and working characteristics of construction machinery, the author finds that there are two main reasons for the above phenomenon. On the one hand, it is caused by poor environment, working conditions and improper maintenance and operation of users. On the other hand, there are some defects in the traditional technology at the beginning of its formation. These technical defects are the fundamental reason for the above phenomenon. Just because these defects have been covered up by the powerful efficacy of loaders, they have not attracted enough attention

with China's entry into WTO and the full implementation of the national strategy of western development. On the one hand, China's construction machinery industry will face more severe challenges, on the other hand, it will also face unprecedented development opportunities. Therefore, it is not only the foundation and guarantee for enterprises to participate in international competition in the future to further strengthen technological innovation, form their own core technology, fundamentally solve and overcome these technical problems that restrict the development of the industry, actively expand and extend the use function of loaders, and make the product technology level in a leading position. It is also one of the directions of enterprise technology development in the future

1. Background of the existing technology

through the understanding of the application technology of loaders, we can find that the overall structure of loaders and the basic structure and working principle of working devices of domestic ZL series, Japanese Kawasaki, American caterpillar and other international well-known enterprises are basically the same

according to the development trend of loader technology at home and abroad in recent years, the first is to develop towards large-scale, and the second is that the internal configuration begins to develop towards the intelligent integration of mechanical, electrical and hydraulic. There is no new breakthrough in the structure of the working device, but it has developed from the original curved arm double rocker to the internationally popular straight boom and single rocker arm "Z" link mechanism, because of the inherent motion and dynamic characteristics of the "Z" reverse link; The unloading is stable and the digging force is large. For example, the "g" loader newly developed by XCMG and Liugong adopts this technology. However, the connecting rod mechanism of the existing working device, whether the forward or reverse mechanism, is composed of two groups of connecting rod mechanisms in series. It usually haunts at night. Therefore, the structural design of the working device basically follows the traditional design idea

2. Defects of traditional technology

the defects of traditional technology are mainly shown through the working characteristics. Through the analysis of the operation process of the loader, we can clearly find these technical defects and the impact of such defects on the whole machine

during the operation of the loader, especially when excavating sand, stone, ore and other objects with large specific weight, the loader often needs to use the engine to provide strong power and repeatedly impact the materials, so as to overcome the operation resistance and make the bucket cut into the pile completely. We can make a comparison with other construction machinery, such as excavators, cranes, hairpin trucks, etc., after adjusting the distance between the upper and lower plates of the bending instrument to 3 times of the measured coil. This kind of machinery mainly relies on the hydraulic system when overcoming the operating resistance, while the shoveling power of the loader completely depends on the output power of the engine. The negative impact of this operating characteristic on the structural performance, reliability and stability of the whole machine is mainly reflected in the following aspects

(1) the repeated impact of the loader during operation makes the fuselage subject to a strong reaction force, which has a great negative effect on the structural strength of the whole machine. Common negative effects are mainly manifested in weld cracking, structural member deformation and so on

(2) this working characteristic makes the engine run at high load for a long time, which has a great impact on the working life and stability of the engine

(3) it has a great negative impact on the fatigue strength of the loader transmission system and the transmission parts in the system

(4) the tire of the loader shall transmit power during operation. The greater the resistance encountered in the digging process, the more likely it is to slip. This phenomenon is not conducive to the working life of the tire

these defects during the operation of loaders are mainly caused by the structural characteristics of working devices. This can be seen from the structural schematic diagram of the traditional working device. As shown in Figure 1, the boom (Figure 1-1) does not help the size of the tunneling force during the operation, but is a steel body that plays a supporting role in the operation

3. The principle and structural characteristics of flexible boom mechanism

the flexible design scheme of flexible boom mechanism is to find problems, clarify objectives and carry out targeted structural innovation through the investigation and analysis of the market and users. The basic principles of mechanical motion scheme are followed

principle and structural features of flexible boom mechanism:

3 2 working cycle: as shown in Figure 2, the bucket is first at the initial position (the place closest to the frame) during operation. The auxiliary boom cylinder extends forward and the driving boom cylinder retracts to make the bucket move in the horizontal direction. After the bucket is fully inserted into the pile, the rocker cylinder extends forward, and the bucket is driven to turn upward through the action of the rocker arm and connecting rod to complete the digging

after the digging is completed, the active boom cylinder is lifted, and the auxiliary boom cylinder is retracted to make the bucket close to the initial position (to avoid forward sinking caused by too long force arm). When approaching the initial position, the main boom and auxiliary boom are lifted at the same time. After the bucket rises to the highest limit position, the rocker cylinder shrinks and drives the bucket to turn down through the rocker arm and connecting rod to complete loading and unloading

after loading and unloading, the rocker cylinder extends forward to drive the bucket to rotate, and the main boom and auxiliary boom retract at the same time to return the bucket to the initial position and complete a work cycle

compared with the traditional technology, the biggest difference of this design scheme is that the boom is composed of two main and auxiliary parts, and a pair of auxiliary boom cylinders are added. The rocker cylinder is not connected with the frame, but with the driving arm. The engine is not completely relied on to provide power during the digging operation. Instead, the engine provides the initial power, and then relies on the work of each cylinder to push the bucket into the material pile

4. Advantages of flexible boom mechanism

the flexible boom mechanism further optimizes the performance of the working device. Its working characteristics are similar to those of an excavator, which can make the bucket realize various composite movements according to a certain trajectory. The operation efficiency and the ability to overcome the resistance in the digging process have been greatly improved. The stress of the structural member is more reasonable, and the impact force on each hinge joint is greatly relieved. It not only helps to improve the stability and reliability of the loader, but also makes great changes in the working characteristics of the loader. The influence of flexible boom mechanism on the overall structure and performance of loader is mainly reflected in the following aspects

(1) the change of working characteristics improves the impact stress intensity and stress frequency of the whole machine during operation, and can greatly improve the reliability of the whole machine structure

(2) the stress of the transmission system and the transmission parts in the transmission system has also been greatly relieved, which has a great protective effect on the working life of the transmission parts

(3) the engine will not run at high load for a long time, which greatly improves the working condition and is conducive to extending the working life of the engine

(4) it effectively avoids the phenomenon of tire slipping when the loader is digging heavy objects, and plays a certain protective role in prolonging the working life of the tire

(5) it can further extend the use function of the loader, broaden the use range, and enable the loader to realize digging, shoveling, raking and various air operations

(6) the unloading distance and height are increased, which can adapt to the loading and unloading operations of various large-scale trucks

(7) the working load of the engine is reduced and the energy consumption is reduced, which meets the requirements of today's environmental protection

5. Function extension

this new type of working device not only changes the original working characteristics of the loader, but also further broadens the functions of the loader. The loader's competitiveness in function, applicability, mobility and other aspects has been fundamentally improved

(1) the flexible boom mechanism can enable the loader to realize the digging function, especially suitable for digging the surface of soft soil

(2) the flexible boom mechanism can make the bucket move horizontally or vertically in the air, and can also make the bucket move at a certain angle. It can realize long-distance loading and unloading, and make the loader competent for various complex large-scale engineering construction

(3) it can make full use of the relative transmission between the auxiliary boom and the active boom to realize raking, digging, shoveling and some aerial operations, which is similar to the function of the excavator in some aspects

(4) compared with the traditional working device, the flexible boom mechanism is more flexible and has a larger working range. The working device is not only suitable for wheel loaders and crawler loaders, but also for the development and design of deformed products of bulldozers and other construction machinery

(5) one machine with multiple functions can be realized by configuring the operation device, which is suitable for railway, wharf, cargo warehouse and other occasions, and has a wider range of application

6. Some problems needing attention in structure

(1) after the main boom and auxiliary boom are fully extended, the force arm is lengthened. Pay attention to adjusting the chassis structure and counterweight of the whole machine

(2) due to the addition of a pair of auxiliary boom cylinders, the structure of the front frame and the distribution of hinge points have been fundamentally changed

(3) the structural design of the boom shall adopt the compound structure as far as possible to improve the structural strength

(4) the boom structure is more complex than before. It has a certain impact on the driver's line of sight during driving and operation, which should be paid enough attention in the structural design of the whole machine

the working device of the loader can be measured quickly. In the structural design, the advantages of other construction machinery should be referred to, and the comprehensive performance of the whole machine should be comprehensively improved through structural innovation. The design idea of flexible boom mechanism is to change the original working characteristics through structural innovation. Its objectives: first, to further improve the shoveling power. The second is to greatly improve the stability and reliability of the loader in the working process. Third, it is necessary to further broaden the functions and scope of use. So as to comprehensively improve the competitiveness of loaders. As a new design idea, the application of flexible boom mechanism needs to be tested in practice

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