Research On Heating And Thermal Simulation Technology Of Automotive Relays

As the switch of automobile electrical system,automobile relay is mainly used in the control,protection,conversion and adjustment of automobile electrical system,and it is one of the most important parts of secondary circuit of automotive electrical system The safety of automobile operation is influenced by the reliability of automobile relay,which is restricted by its thermal characteristics of heat and heat dissipation.In addition,with the popularity of hybrid electric and new energy vehicles,the requirements of automotive electrical system for automotive relays are gradually increasing.which requires the development of automotive relays towards miniaturization and high-load,so the requirements for thermal field design of automotive relays are more and more demanding.In order to assist the thermal field design and optimization of products,it has an important engineering practical value to establish a reasonable and credible numerical simmlation model to study and analyze the thermal characteristics of automotive relays.This paper takes a type of automobile relay produced by Xiamen Hongfa Automotive Electronics Company as the research object,builds an iterative coupling simulation model of electricity-heat flow multi-physical field of automobile relay,and studies and analyzes the characteristics of heat and heat dissipation of the relay.The specific contents include the following parts:Firstly,by using the mumeri cal analysis software and the theories of electronics,numerical heat transfer and computational fluid mechanics,and considering the actual heating and cooling process of the relay,contact resistance of the contact,and external wires of the relay,the iterative coupling simulation model of the electric-heat flow multi-physical field of the automobile relay was established.The model is used to calculate and analyze the current field,temperature field and airflow field of the relay under 9 working conditions of load current of 10 A,20A,30A and ambient temperature of 30? 85? and 125?,respectively.According to the requirements of temperature rise test of electromechanical relay,the temperature rise test of this type of automobile relay is carried out.In the test,the temperature rise of coil,dynamic/static pin measuring point and housing surface is measured respectively by means of resistance method,thermocouple sensor and thermal imager.By comparing the measured and simulated data,the error of simulation is between-7.56%and 8.86%,which indicates the accuracy of the simulation model.And this model can provide reference for the thermal field design and optimization of related relay products,especially the large-load relaySecondly,by establishing the sequence coupling model of electric-heat flow and the finite element model of solid thermodynamics,and using the corresponding temperature rise test as the comparison benchmark,the model was compared with the electric-heat flow iterative coupling model under the same working conditions,and the rationality and accuracy of the established iterative coupling model of electric-heat flow were verified.By comparison,it can be seen that under high-load or high-temperature conditions,if the electric-heat flow sequence coupling model is adopted,which does not consider the influence of the inhomogeneous temperature of the conductor on the heating power of the load loop,the temperature simulation value will be far less than the actual value.In addition,if the solid thermodynamic finite element model is adopted,which does not consider the influence of air heat conduction in finite space inside the relay and air convection heat transfer in large space outside the relay on the temperature distribution on the shell surface,the simulation results of the shell surface temperature distribution will differ greatly from the actual resultsThirdly,the established electric-heat flow iterative coupling numerical simulation model is used to analyze the influence of three factors,including load current,ambient temperature and plastic material,on the temperature field of automotive relays.The simulation results can be used as the reference for setting the product operating conditions of automotive relays and selecting plastic materialsFinally,according to the analysis of the thermal failure phenomenon in the accelerated durability test of this type of automobile relay,the structure of the thermal failure point is optimized,and the optimization scheme is designed to improve the sample.By comparing with the conventional samples in parallel temperature rise test,the improved samples' thermal failure point temperature rise decreased by 5.83K on average,which verified the effectiveness of the optimization scheme.