Shearer cutting part is a multi-stage gear transmission system supported by rocker box, which has many parts and complex structure. At the same time, due to the special geological conditions of coal mine, the roller load has the characteristics of heavy load and strong impact, and the cutting part is in the condition of variable speed and variable load for a long time. The above factors make the dynamic behavior of the cutting part complex and the faults occur frequently. Aiming at the existing problems, the main research contents are as follows:
① Modeling of multistage gear system under large deformation
The existing research on the dynamic modeling of shearer cutting part is over simplified, which can not reflect the structural characteristics of the cutting part with flexible cantilever box and multi-stage gear transmission. In this paper, the dynamic modeling of cutting part is summarized as the modeling problem of multi-stage gear system under large deformation, and innovative work is carried out in two aspects: gear meshing excitation modeling and transmission system box coupling dynamic modeling. The slice calculation method of meshing excitation is improved, and the influence of system deformation on meshing angle and actual meshing interval is considered. The simulation accuracy of gear dynamics under the condition of three-dimensional large deformation is improved. Aiming at the problem of complicated dynamic modeling of multi-stage gear system, an efficient general modeling method based on matrix operation is proposed. Based on the above theoretical research and considering the coupling relationship between motor gear drum gear shaft bearing box, the finite element lumped parameter hybrid dynamic model of the cutting part of a mg1200 shearer is established.
② Analysis of coupling characteristics of multistage gear transmission and case
The existing research is lack of in-depth study on the influence of shearer rocker box on the dynamic characteristics of cutting transmission system. The natural vibration characteristics of rocker box, multi-stage gear transmission and multi-stage gear transmission coupling system are calculated respectively. The influence of coupling rocker box on the natural vibration characteristics of multi-stage gear transmission is analyzed by using the characteristics of natural frequency, vibration mode and modal strain energy. Then, the dynamic deformation, dynamic load and vibration acceleration of the system at different speeds are solved, and the influence of the rocker box flexibility on the dynamic simulation results is analyzed.
③ Dynamic characteristics of cutting unit under variable load condition
The coal rock properties of different coal mines are very different, and the load of shearer drum is complex and changeable. The existing research lacks the research on the influence law of the drum load on the dynamic response of the cutting part, which may lead to the unknown dangerous response of the cutting part in use. In this paper, steady-state and transient response characteristics of the cutting part are studied respectively under steady load and impact load. The effects of load coefficient and load fluctuation coefficient on gear meshing state and rocker box vibration characteristics are analyzed under steady load. The differences of simulation results with different gear dynamic models are compared, and some analysis conclusions are verified by experiments. The transient response of the cutting part is simulated under the impact load, and the weak links of the cutting part are identified by combining time-frequency analysis and modal strain energy analysis.
④ Dynamic performance improvement of cutting part
The ultimate goal of dynamic analysis is to design object products with high dynamic performance. In this paper, 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. The deformation of the rocker box is an important reason for the eccentric load of the internal gear transmission. Through the structural optimization of the rocker box, the deformation of the box and the eccentric load of the tooth surface under the steady load and impact load are reduced. The meshing impact and partial load of gear surface are the key causes of system vibration and premature damage. A three-dimensional topology modification method of multi-stage gear considering box deformation is proposed, which can significantly reduce the peak value of contact stress and dynamic load coefficient of each gear pair under rated working condition.