| In recent years,gear transmission has developed towards high-speed and heavy-load.The influence of the friction heat generated in the transmission process due to the relative sliding between two meshing tooth surfaces on the performance of the gear transmission system can not be ignored.At present,the research in this field is mainly focused on the single field state performance of system,such as the static characteristics,dynamic characteristics and thermal characteristics.However,the study on the interaction between thermal and statics or dynamics properties is neglected.In this paper,based on the theory of gear meshing,tribology,heat transfer,elastic theory and thermo-elastic theory,the influence of heat on the performance of gear transmission system was studied by means of numerical calculation,finite element simulation and experimental research.Then the fuzzy design and other modern design methods were used to design the gear teeth with multi-objective comprehensive tooth profile modification.The main contents are as follows:(1)Based on the theory of tribology and heat transfer,the heat generation and heat transfer mechanism in gear meshing process were investigated,and the thermal characteristics of gears such as the gear surface flash temperature,bulk temperature field and tooth surface instantaneous contact temperature were studied.The influence factor and influence mechanism of each thermal characteristic were also studied.At the same time,the influence of tooth profile modification on each thermal characteristic was studied,and the optimal tooth profile modification parameters with each thermal characteristic as a single obj ective were obtained.(2)Based on Hooke’s Law and Hertz contact Theory,the definition of gear stiffness was generalized,and the thermal stiffness of gear was defined as the value of the external load which causes the unit thermo-elastic coupling deformation amount.Combined with the research results of the thermal characteristics of the gear transmission system,the formulas for calculating the single tooth thermal stiffness and meshing thermal stiffness of the gear were derived and verified by the finite element method.Meanwhile,the influence of tooth profile modification on the thermal stiffness and influence of heat on the static characteristics of the system were also studied.(3)The thermal dynamic characteristics of the gear transmission system under thermo-elastic coupling condition were studied.Based on Coulomb damping model,the equivalent viscous damping model of gear transmission system was established.Considering the effect of heat on lubricating oil,the calculation method of equivalent viscous thermal damping of the system was obtained.By introducing the time-varying meshing thermal stiffness and equivalent time-varying viscous thermal damping,the thermo-elastic coupling dynamic model of the gear transmission system was established.The thermal dynamic responses of the system were obtained.The effects of damping and rotational speed on the thermal dynamic characteristics of the system were studied.Meanwhile,taking the tooth profile modification as part of the system static error,a new modeling method of system dynamics after tooth profile modification was proposed,named "Equivalent static error method".Then the thermo-elastic coupling dynamic model of the system after tooth profile modification was established.The thermal dynamic characteristics of the system after tooth profile modification were also obtained,and the optimal tooth profile modification parameters under the condition of thermo-elastic coupling were obtained.(4)The static characteristics,dynamic characteristics and thermal characteristics of the system are comprehensively considered,a multi-objective comprehensive modification method for gear teeth was proposed.A multi-objective comprehensive modification model of gear teeth was established by using the fuzzy comprehensive decision method.At the same time,in order to get more general results,the influence of geometry and working condition parameters on the multi-objective comprehensive modification model was studied.The correction coefficient Xc of the tooth profile modification amount under the multi-objective condition was introduced.Then the formula of the tooth profile modification amount under the multi-objective condition was given,and the comprehensive optimal tooth profile modification parameters of gear tooth were obtained.(5)Based on FZG gear tester,the thermal vibration test platform of gear transmission system was set up,and the experimental research on gear transmission system was carried out.The thermal and dynamic characteristics of the system under various integrated working conditions such as different loads and different rotational speeds were tested.Based on the test data,the influence of load and rotational speed on the thermal and dynamic characteristics of the system was studied.At the same time,by extracting the dynamic response of the system under different temperature conditions,the influence of heat(temperature)on the dynamic characteristics of the system was studied. |
