| Shifting clutches are the key components to realize dynamic shift in integrated transmission device,which are often damaged a nd distorted because of excessive thermal load during the engaging process and then directly affect the transmission system reliability.Therefore,it’s significant to study and analyze the thermal equilibrium of the relationship between heat production and heat dissipation.In this study,a theoretical model of clutch hydraulic system is proposed to investigate the influence factors of temperature rise of wet clutch.A shifting dynamic model of integrated transmission is proposed to analyze the characteristics of the heat load of different shifting frequencies and coefficient of resistance.Furthermore,a formula is proposed to predict temperature rise of clutches at different shifting frequencies.Main scientific work in this research is shown as follow:Firstly,a thermal resistance network model of the clutch hydraulic system is proposed to investigate the effects of oil flow and rotation speed difference on the temperature rise of wet clutch during engaging by Simulink.The results show that the oil flow rate has a greater influence on the temperature rise of wet clutch under the condition of high heat flux than that under the condition of low heat flux.The oil flow brings a slight effect on temperature rise when the cooling flow exceeds the critical value.Secondly,the simulated solution of a six-degree-of-freedom elastic dynamic model is obtained by AMESim,and the temperature rise characteristics of clutches during shifting are investigated.The relative error between the simulation results and the theoretical results is within 10%.Thirdly,a mathematical model of the shifting frequency of a tracked vehicle is proposed to investigate the average temperature rise of the wet clutch.The shifting frequency per hundred kilometer is obtained by considering coefficient of resistance,including plain,plateau and hot-humid region.The temperature of the wet clutch continuously increases as shifting frequency increases.In addition,a formula is proposed to predict temperature rise of clutch by comparing the e ffect of the shifting frequency on temperature rise in different regions.In order to avoid the clutch failure high speed tracked vehicle,it is recommended that the shifting frequency should be less than 14.Finally,a test bench is designed to validate the simulation results.The no load power and the temperature of the clutch system under different oil flow and different rotation speed difference are measured,respectively.The experiment and the simulation results agrees wel,which validates that the theoretical analysis. |
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