| Dry clutches are widely used in automotive transmission due to its high transmission efficiency and simple structure.However,intensive temperature rise during clutch slipping phase,especially in the frequent starting and shifting conditions,resulting in the performance degradation of friction disc and transmission capacity reduction of the clutch.Above all,it is rather important to study the temperature field of a dry DCT during frequent slipping.Finite element analysis is an effective means to study the clutch temperature field.The current research mainly use the uniform pressure assumption and uniform wear assumption to model the heat flux distribution on the friction surface.Due to the structure of clutch,the diaphragm spring push the pressure plate with the separation finger only,and the pressure near the separation finger is relatively high.This thesis measured the actual pressure distribution on the friction surface of a dry clutch.And a nonuniform pressure distribution model and corresponding heat flux model are established based on the measured result.According to heat transfer theory,the heat differential equation of the dry clutch as well as its initial conditions and boundary conditions were established.After that,a 2-D finite element thermal model of the main clutch was established with the software ANSYS.In order to study the influence of non-uniform pressure distribution on heat transfer model,the nonuniform pressure model was used to simulate the thermal model and the result was compared with the result of uniform pressure model and uniform wear model.In order to verify the proposed non-uniform pressure model,a bench test was carried out to measure the temperature distribution of dry clutch during the slipping process.The experimental results show that the nonuniform pressure distribution model is closer to the actual results.Compared with the traditional uniform pressure model and uniform wear model,the results of the non-uniform pressure model are more suitable for clutch design and overheat protection. |
