With the continuous increase of mining depth, the geological characteristics of high ground stress and strong mining disturbance in deep coal seam make the operation task of shearer more complex. Shearer cutting part is a multi-stage gear transmission system with cantilever box. Its complex structure and frequent faults seriously restrict the production efficiency and economic benefits of fully mechanized mining face. In this paper, the research work is carried out from four aspects: modeling of multi-stage gear system under large deformation condition, analysis of multi-stage gear transmission box coupling characteristics, dynamic characteristics of cutting unit under variable load condition, and improvement of dynamic performance of cutting unit
① The dynamic modeling of shearer cutting part is summarized as the problem of multi-stage gear system modeling under the condition of large deformation. Aiming at this problem, the general modeling method of large deformation gear model and multi-stage gear system is proposed. In the large deformation gear model, the slice meshing excitation algorithm is improved, and the influence of system deformation on meshing angle and actual meshing interval is considered, which improves the simulation accuracy of gear dynamics under the condition of large deformation. The general modeling method of multistage gear system takes the dynamic substructure method as the core. On the basis of the standardized programming of the key steps of system substructure decomposition and local / global degree of freedom transformation, the automatic assembly of substructures is realized by matrix operation. Based on the above theoretical research, the multi-stage gear transmission box coupling dynamic model of a mg1200 shearer cutting part is established.
② By means of natural vibration analysis and system dynamics simulation, the coupling dynamic characteristics of multi-stage gear transmission and rocker box are revealed
1) The natural vibration characteristics of rocker box and multi-stage gear transmission are calculated respectively. The natural frequency and vibration mode of the rocker box (condensation model) are calculated by programming, which is in good agreement with the calculation results of the finite element software, indicating that the box condensation is correct. The modal of multi-stage gear transmission is calculated, and the natural frequency of torsional vibration mode is extracted.
2) Based on the characteristics of natural frequency, vibration mode and modal strain energy, the natural vibration characteristics of multi-stage gear transmission box coupling system are analyzed. The results show that the natural frequency of torsional vibration mode of multi-stage gear transmission decreases to a certain extent after coupling the rocker box.
3) It is found that in the non resonance region, the effect of coupling rocker box is mainly to increase the eccentric load of gear pair, but has no obvious effect on the dynamic load of gear pair; in the common vibration region, the dynamic meshing force of multi-stage gear transmission reaches the peak (resonance) after coupling rocker box The rotating speed of the engine is reduced to a certain extent.
③ The dynamic response characteristics of shearer cutting part under variable load condition are analyzed, and some conclusions are verified by experiments
1) It is found that when the load coefficient increases from 0.2 to 1.8, the change of meshing frequency of each gear pair is small, and the peak value of meshing error is approximately linearly related to the load coefficient and load fluctuation coefficient of drum load.
2) It is found that with the increase of the load factor, the overall vibration intensity of the rocker box increases approximately linearly, but the variation trend of the vibration acceleration at different measuring points (or even in different directions of the same measuring point) is different.
3) The transient response of the cutting part under impact load is analyzed. It is found that the transient response of the rocker box vibration is dominated by the low-order mode of the coupling system, the transient response of the torsional vibration of the multi-stage gear transmission is dominated by the first non-zero frequency torsional vibration mode of the coupling system, and the impact energy is mainly concentrated on the elastic torque shaft at the motor end, the elastic torque shaft at the roller end, and the second stage planetary gear train.
④ The dynamic performance of shearer cutting part is improved from two aspects of rocker box structure optimization and multi-stage gear three-dimensional topology modification
1) In order to improve the low-order natural frequency, the structure of the rocker box is optimized, and the deformation of the rocker box and the meshing error of the gear pair are significantly reduced under the steady load and impact load.
2) Combined with system dynamics simulation and fine tooth contact analysis, a new method of multi-stage gear 3D topological modification is proposed. By using this method, the peak value of contact stress and dynamic load coefficient of each gear pair in the cutting section under rated working condition are significantly reduced.
⑤ In this paper, the research results of dynamic characteristics analysis of transmission system and multi-stage gear three-dimensional topology modification under the condition of large deformation of rocker box of cutting part have been applied in Taizhong Coal Machinery Co., Ltd., which provides effective theoretical methods and technical means for the pre research of M1200 shearer and the technical transformation of M129 shearer.