Research On Thermal Reliability Of ECU For Electronic Controlled Diesel Engine

With the rapid development of automotive electronic technology,there are more and more function modules in the engine ECU,and the integrated chips,especially the power devices,become more and more complex.These changes will lead to a great increase in the power dissipation per unit volume of the PCB,which will generate a lot of heat in the process of operation.The local temperature of the circuit board will be too high unless these heat can be released in time,which will lead to the failure of some components,and the decrease of the thermal reliability of the circuit board.Therefore,research on thermal reliability of ECU for electronic controlled diesel engine will be carried out in this paper,which will conduct thermal simulation analysis and experimental research.In the aspect of thermal simulation analysis,the thermal simulation model of diesel engine ECU is established by FloTHERM firstly.And then,the ECU temperature test platform is designed and built to validate the thermal simulation model.The results show that the relative error between the temperature simulation results and the test results of the key components in ECU is less than 8%,which meets the requirements of engineering analysis.Simulation analysis on factors which have great influence on the temperature distribution of ECU,such as environmental temperature,altitude,working conditions,is carried out to find the temperature variation law of components.It show that the highest temperature area of ECU is mainly concentrated in power supply module,MCU module and drive module.And the temperature of components increases linearly with the increase of ambient temperature.What is more,without considering the change of ambient temperature,every 1000 m elevation will increase the temperature of components by about 0.7 C.In addition,the temperature of the components will be the highest when the working condition is mode5,and the components greatly affected by the working condition mainly concentrate on the power supply module and the fuel injection drive module.Besides,the temperature of ECU decreases greatly after introducing liquid cooling,and the higher the flow rate of cooling liquid and the lower the inlet temperature,the better the cooling effect will be.According to the thermal simulation results,the thermal reliability test scheme based on the performance degradation distribution of ECU functional modules is designed.Firstly,the variation law of performance parameters of each module of the ECU with time is obtained by accelerated life test.And then,the thermal reliability of the ECU is studied from two aspects of module and whole.The results show that the reliability of power supply module and MCU module is basically the same,and the life expectancy is about 62,000 hours and 63,000 hours respectively when the failure threshold is 10%,while the thermal reliability of driving module is lower,whose life expectancy is only 25,000 hours.Moreover,it can be concluded that the working temperature of the three modules cannot exceed 368K,368K and 318K respectively if the design life is 10000h and the failure threshold is 10%.Therefore,the reasonable layout or other effective heat dissipation design of each module can be carried out by thermal simulation analysis in the design stage of ECU circuit so as to control the temperature of each module and improve the service life of the ECU.