| The shifting clutch is an important transmission component of the Hydraulic Mechanical Continuously Variable Transmission(HMCVT).Controlling its engagement and disengagement can realize the switching of the stages.The shifting clutch relies on the contact friction between the friction plate and the mating rigid plate to transmit power.With the help of hydraulic oil to cool and lubricate the friction surface,it is inevitable that there will be drag torque and heat problems,which will cause belt and row loss and friction pair temperature field.The change is very likely to affect the power transmission efficiency and cause thermal failure.Therefore,it is meaningful to make drag torque analysis and thermal analysis in the working process of the shifting clutch.This article mainly designs the friction pair of the HMCVT shifting clutch,and explores the drag torque of clutch and the law of temperature changes during idling and engagement.The specific work content is as follows:(1)Design friction pairs and make 3D model.According to the results which the laboratory has had,combined with design requirements and actual needs at the time,I design the relevant structural parameters(The inner and outer diameters of friction plate and sheet steel,separation gap and so on.)and working parameters(hydraulic oil flow,etc.)of the friction pair.Then establish a three-dimensional simulation model of the friction pair and the oil layer between them by using the three-dimensional software called CATIA.(2)Improve the mathematical model of belt-displacement torque and analyze the relationship between clearance,speed,flow rate.Use the actual viscous fluid momentum equation in the foundation of fluid dynamics to improve the traditional drag torque prediction model.Through the relationship between flow rate and equivalent radius,the influencing factor,oil flow,is introduced and it improves the problem of ignoring the influence of centrifugal force at relatively high rotating speed in the traditional model,which also improves the accuracy and rationality of prediction;three main factors that affect the t drag torque are proposed: the flow of cooling lubricant,the relative speed of the friction pair,the clearance of the friction pair.MATLAB performs calculation and analysis to explore the relationship between these three factors and the change of drag torque.(3)Take heat-fluid coupling finite element simulation of idling process.Taking the oil film between the friction pairs as the research object,using ANSYS/Fluent to analyze the heat flow coupling of the clutch idling process.Based on the simulation results,study the relationship between cooling lubricant flow rate,the relative speed of the friction pairs,the separation gap and the gas-liquid two-phase between the pairs.Comparing the drag torque values obtained from the mathematical model and the simulation model,verify and analyze the rationality of the model,and explain the drag torque variation law furtherly.At the same time,make analysis on the influence of relative speed,separation gap and oil flow on the temperature rise of oil film during idling.(4)Take thermal-structural coupling simulation of the bonding process.Establish a simplified finite element simulation model of the friction pair of the shift clutch and use ABAQUS to conduct thermal-structural coupling simulation analysis on the friction pair of the shift clutch in the engagement stage.Based on the temperature field cloud diagram of friction pair obtained by simulation and the temperature variation curve of friction pair at different radius nodes with time,explore the temperature variation rule of friction pair in the process of clutch engagement.(5)Set up a test bench for the shifting clutch,design a real-time measurement system for the temperature of the steel sheet and conduct a temperature rise test for the friction pair engagement.The wet multi-plate clutch is filled with oil,and the friction pair rotates at a high speed during the working process.It is difficult to measure the temperature of the friction plate directly,while the traditional method of measuring the oil temperature has large error.Therefore,in view of the complicated internal environment,a brand-new design of sheet steel temperature measurement is carried out,and the relevant sensors and other hardware are selected or calibrated in advance.The temperature measurement experiment of the sheet steel during the engagement process was carried out through the wet clutch test bench.Change the engagement pressure and relative speed during the working process in order to analyze the influence of different working conditions on the temperature rise. |
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