Analysis And Experimental Study On The Vehicle Engine Starting System Under Low Temperature

Starting performance of engine is an important parameter that decides quality or not.The vehicle engine meets the needs of a reliable starting system that can smooth start under low temperature.This paper takes the starting system of SOFIM diesel engine as a study object, main influencing factors of starting vehicle under low temperature are general analyzed,such as different environment temperature,structure parameters of starter motor,storage capacitance of battery etc.Electromagnetism theory is used to establish running character and magnetic simulation model of the starter motor,the influencing factors of starter motor's structure are analyzed and calculation formulas of starter motor's structure are confirmed.The influences of electrolyte density to starting voltage of battery at different environment temperature are analyzed by experiment. The relation between the starting process parameters of diesel engine and environment temperature is discussed.Using PMDC as a study object,the influence of many structure parameters to performance of starter motor is general analyzed,such as its armature effective calculation length,pole-arc coefficient,air gap thickness,stator pole's number etc. The starter motor running character model is designed,ideal no-load character and magnetic field are simulated by Ansoft EM software,The result shows that:when the voltage keeping constant,the temperature decreases from 30℃to -35℃,the starter motor output torque,speed and power increase with armature current increasing; when temperature keeping constant,voltage decreasing,starter motor output torque, speed and power decrease with armature current increasing.The influence of a single structural parameter to characters of starter motor is analyzed;and distributed condition of magnetic field of starter motor.The structure parameters are optimized by using the Quasi Newton law,and the no-load character of starter motor is improved.The match on starter motor has been carried out at -18℃～-25℃.The influencing factors on storage battery capacitance are analyzed,such as its ply structure,starting voltage and current under low temperature.The relation between starting voltage and starting current of storage battery with starting time at -25℃is discussed,the results show that:decreasing ply thickness,increasing ply height and improving electrolyte density can be propitious to improve battery capacitance.The starting performance of SOFIM diesel engine under low temperature has been studied by experiment.The relation between starting resistance torque and environment temperature under different engine speed has been investigated.The results show that the environment temperature decreases -5℃,starting resistance torque increases 2.5N.m as speed keeping constant;speed above 170r/rain,enhances 50r/min,starting resistance torque increases 3～8 N.m.