The cutting part is the core part of the shearer’s function of cutting coal and loading coal. It is mainly composed of cutting motor, cutting transmission system, cutting drum, rocker arm box and accessory device (lubrication, spray, cooling device). The rocker box is a hollow cantilever structure, which not only supports the normal operation of the internal cutting transmission system, but also bears a huge roller load at the free end. Cutting transmission system generally adopts two-stage fixed shaft gear plus two-stage planetary gear train, or three-stage fixed shaft gear plus one-stage planetary gear train. The output power of the cutting motor reaches the cutting drum after the reduction and torque increase of the fixed shaft gear and planetary gear train. The typical structure of the cutting part is shown in the figure. The cutting drum is designed with pick and spiral blade to realize the functions of cutting and loading coal respectively.
From the perspective of dynamics, the cutting part is a multi-stage gear transmission system supported by cantilever box, which has complex dynamic behavior. It consumes more than 80% of the power of the whole machine and is the weak part of the shearer. Statistical data show that the failure rate of cutting part of mg650 / 1620-wd Shearer in a mine is 46.15%, which ranks the first; the failure rate of cutting part of joy-7ls07 Shearer in a mine is 46.15% 3%, and the failure rate ranks the first; among all the failures of an imported shearer used in a mine for seven years, the failure rate of the cutting part accounts for 34.2%, and the failure rate ranks the first. Among them, the transmission system accounts for the highest proportion of the total fault number of the cutting part, especially the gear fault.
Coal seam is the cutting and crushing object of shearer, and its physical and mechanical properties have an important impact on the drum load and service life of shearer. Coal is formed by the sediment of ancient geological period through a long process of carbonization and metamorphism. The physical and mechanical properties of coal and the structure of coal seam are greatly different due to different original sediment, different degree of carbonization and metamorphism, and different regional geological movement. The cutting resistance of coal ranges from 30 n / mm to 420 n / mm, which can be roughly divided into soft coal, medium hard coal and hard coal. For the pure coal with specific cutting resistance, the drum load fluctuates randomly due to the anisotropy and brittleness of coal. For the real coal seam, it generally has complex and difficult to fully explore the bedding and joint characteristics. For example, one or more banded rock intercalations are called gangues; other irregular hard minerals scattered in coal seams are called hard inclusions. The position of these impurities in the coal seam is irregular, their own shapes are different, the specific number is unclear, and they have great randomness. In addition, in the actual production process, the shearer operators rely on the way of seeing and listening to adjust the drum height, inevitably cutting to the roof and floor, which makes the drum load suddenly increase. To sum up, the drum load of Shearer has the characteristics of strong randomness and strong impact.
With the decrease of shallow resources and the transformation of China’s economy to high-quality development stage, coal mining is developing towards deep and intelligent direction. The geological characteristics of high ground stress and strong mining disturbance in deep coal seam make the working environment and task of shearer more complex, and put forward higher requirements for the reliability of the cutting part. At present, the design of China’s high-power shearer is mainly completed by analogy with the large-scale shearer imported from abroad. However, the coal and rock properties of domestic and foreign coal mines are very different, and there are many problems in the actual use process. Therefore, to improve the level of energy equipment, we must take the road of independent design. Different from the general gear system, the shearer cutting part has the following working conditions and structural characteristics: 1) due to the complex geological conditions of coal mine, the load of the cutting part has strong randomness and strong impact; 2) with the development of the shearer towards the direction of high power, and the drum speed required by the fully mechanized mining technology is low, so the cutting transmission system is a kind of low-speed and heavy-duty gear transmission device; 3) rocker The arm box is a hollow cantilever structure, which will produce large deformation under the huge roller load and affect the gear meshing state of the internal cutting transmission system.
The above characteristics of the cutting unit bring great challenges to the independent design and safe operation. If we can not fully grasp the dynamic characteristics of the cutting unit under various possible working conditions in the design stage, and carry out targeted design, it is very easy to cause premature damage and threaten the reliable operation of the shearer and even the whole working face. Therefore, it is of positive significance to carry out the dynamic modeling analysis and dynamic performance optimization research of multi-stage gear transmission box coupling of shearer cutting part for improving the working performance of cutting part and realizing high yield and high efficiency of fully mechanized working face.