| Scraper conveyor is the key equipment in fully mechanized coal mining face and its transmission process is pivotal to its steady operation.The working ability and reliability of scraper conveyor chain drive system directly affect the safety and production efficiency of modern coal mining industry.In recent years,the shutdown accidents which are caused by the faults of components in the drive system have occurred frequently and the accidents are closely related to the timevarying load on the drive system during operation.In order to guarantee the safety of mining process,it is of great importance to investigate dynamic fluctuation characteristics of scraper chain drive system.In this paper,methods of combining theoretical research,experimental test,simulation calculation and statistical test were used to describe the time-varying characteristics of scraper chain drive system from different sides by taking the speed,acceleration and force fluctuation characteristics of scraper chain as main research objects.The purpose of this subject is to provide some guidance for the process improvement and design optimization of scraper chain drive system.One-side contact model and two-side contact model were established to analyze kinematics characteristics of scraper chain drive system and the models are suitable for the speed and acceleration analyses of scraper chain in the sections of nose and tail respectively.Combining meshing characteristics and general force situation of scraper chain at different positions,calculational formulas of chain tension in rectilinear motion period and meshing period were deduced respectively.After comparing the experimental data with the theoretical values,the rationality of the kinematics models is verified and the applicational scope of the tension formulas is clarified.Based on the fundamental theories of contact mechanics,effects of several factors on meshing contact of drive system were investigated and the factors include pitch of chain,curvature radius of chain arc and relative sliding between chains.Based on the linear damage accumulation model and the results which were obtained by experiments and simulations,fatigue life of chain ring was evaluated by using rain flow counting method.A rigid-flexible coupling dynamic model of chain drive system was established by using ADAMS.After recognizing stress images of element nodes of the flexible chain ring,the position information of the maximal stress point in this ring is obtained.When the horizontal ring transits from rectilinear motion period to meshing period,the region where the maximal stress lies transfers from ring-ring contact zone to sprocket-ring contact zone and the value of stress increases accordingly.Besides,time histories of chain speed,contact forces between chains and meshing force under different driving modes,inclination angles,laying lengths,driving rotational velocities and load conditions were calculated and described by taking multi-rigid-body dynamics models as simulation models and variate controlling method as principle.In addition,the reasons why fluctuation characteristics of scraper chain drive system vary under different parameters were dug out.Finally,a simulation plan was designed on the basis of orthogonal experiment.Some conclusions are obtained when using coefficient of variation as the index to evaluate the fluctuation stability of contact force between chains and meshing force between sprocket and chain.The simulation results which are aiming at distinguishing the primary-secondary property and significances of factors including inclination angle,laying length and driving rotational velocity are processed by range analysis and variance analysis.The results show that driving rotational velocity plays the most significant influence on fluctuation of both forces,inclination angle plays a relatively significant influence on fluctuation of contact force and laying length plays a relatively significant influence on fluctuation of meshing force. |
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