Research On Dynamic Characteristic And Time-dependent Reliability For Multi-stage Herringbone Gearbox With Planetary Gear Sets

With the exhaustion of shallow coal resources,coal mining is extending to the depth below 1km,and the risk coefficient of mining is significantly increased.Disasters,such as thermal damage,rock burst,coal and gas outburst,water permeability,mine pressure and coal seam natural disasters,don't only increase the difficulty of mining,but also increase the cost of mining.It is urgent to adopt unmanned intelligent mining technology to keep miners away from dangerous and harsh working environment and improve coal mining efficiency so as to finally achieve the purpose of “ensuring safety,reducing disasters and improving efficiency through unmanned management”.However,in order to realize unmanned intelligent mining instead of human labor,it is necessary to ensure that intelligent mining equipment can work continuously and reliably for a long time under complex working conditions.So,it is necessary to solve the heavy-duty coal mining equipment reliability and high performance transmission technology.The shearer cutting section is the core device for coal cutting and loading.Its performance directly affects the cutting efficiency of coal seam and the reliability of heavy-duty mining equipment.The traditional rocker arm gearbox with straight tooth or helical tooth transmission is very bulky,and likely to cause rocker arm deformation,which will increase errors in rocker arm gearbox transmission system,and deteriorate working conditions so that the failures of the cutting part gearbox is accelerated.In order to ensure enough radial stiffness,and control radial deformation within the scope of the license to achieve the goal of improving life and reliability of shearer,compacting structure,larger power weight ratio of herringbone gear and planetary transmission characteristics,a three-stage herringbone gear box with a planet transmission is proposed in this dissertation to meet lightweight and high performance transmission of gear box of shearer cutting section,and a comprehensive in-depth study will be carried out for dynamic characteristics and reliability of this new type of multistage herringbone gear box under the action of random load.Therefore,the main research contents of this dissertation are as follows:1.Dynamic model and analysis of multi-stage herringbone gear transmission with a planetary transmission under complex working conditionsAccording to the meshing principle of herringbone gear,a dynamic model of multi-stage herringbone gear transmission with planetary transmission is established by taking into consideration the influence factors,such as bearing deformation,meshing stiffness,meshing error and tooth side clearance.The dynamic characteristics of multistage herringbone gear system under random load were solved by Monte Carlo and numerical calculation method,and the random processes of bending and contact stress of each gear and the stress of each bearing were obtained.The dynamic characteristics obtained from the calculation are analyzed.In addition,the influence rules of system structure parameters,manufacturing errors and other factors on the dynamic performance are studied,and the effective measures to improve the working performance and reliability of multistage herringbone gear box are explored.2.Dynamic reliability model and analysis of a multi-stage herringbone gear transmission with a planetary transmission considering failure correlationAccording to the principle of fatigue damage,the strength calculation model of parts is established to obtain the random strength process of key parts of the transmission system by considering the strength degradation.According to the theory of stress-strength interference,the reliability model of parts with random process stress and strength is established.Correlation coefficients are used to indicate the relevant relationship between different failure modes,and according to the value of the correlation coefficient between different failure modes,the failure modes are divided into different failure mode groups,which are mutually independent,and then the dynamic reliability model of multistage herringbone gear transmission is established.The influence of the internal excitation of multistage gearbox,the time-varying distribution parameters of component strength and dynamic force,and the correlation of failure modes of gearbox components on reliability are studied by analyzing the reliability of the rocker gear dynamic coal winning machine cutting part under the action of the random load.And it lays a foundation for the subsequent reliability optimization design.3.Model and analysis of dynamic reliability sensitivity of the multistage herringbone gearbox with a planetary transmissionAccording to the relationship between the system parameters and the reliability in the dynamic reliability model,the reliability sensitivity function of the variation of the reliability with the system parameters is derived from the ?R/?Xi)(where R is the reliability,Xi is a design parameter,and Xi?X,X is the design parameter vector).The numerical methods,such as the moment method or important sampling method,are used to obtain the sensitivity of the gearbox reliability,analyze the influence law of system parameters on the reliability,and find out the main parameters that have significant influence on the reliability of the system,so as to provide the basis for the subsequent reliability optimization design.4.Multi-objective reliability optimization of the multistage herringbone gearbox with a planetary transmissionThe multi-stage herringbone gearbox with planetary transmission has a complex structure and multiple design parameters and it is often used in complex working conditions and occasions with large power.In order to guarantee the system reliability,improve the dynamic characteristics,realize the lightweight,and lower the manufacturing cost and resource consumption,a reliability optimization design model for a multistage herringbone gear is established.And in this model design variables include transmission ratio,gear teeth,modulus,tooth width at all levels,the meshing angle,helical angle,etc.The optimization goals include dynamic performance,reliability and reliability sensitivity,volume of driving medium,etc.The constraint conditions include strength,meshing condition of parallel shaft herringbone gear transmission,transmission ratio,number of gears,and number of planetary wheels,concentric condition and assembly condition of herringbone gear planetary transmission.The reliability optimization design model is solved to obtain the multi-level herringbone gear box optimization design parameters by MATLAB multi-objective genetic algorithm function.According to the optimized parameters and dynamic model,the dynamic characteristics after optimization are calculated and compared with those before optimization to verify the correctness of the optimization method.5.Experiment and analysis of dynamic characteristics of the multistage herringbone gearbox with a planetary transmissionAccording to dynamic characteristics and data collection requirements of the testing principle,a general scheme for testing the dynamic characteristics of multi-stage herringbone gear box of shearer arm is put forward.Based on the similarity principle,the performance parameters of the test platform are determined and the test platform for dynamic characteristics is built.Besides,the dynamic characteristics of the multi-gear box under constant speed step load,impact load and random load are tested,and the dynamic characteristics of the multi-gear box under random load with different service time are tested and the probability statistical characteristics are analyzed and the correctness and validity of the dynamic model is verified.