Typical Fault Analysis And Test Research On Crankshaft Front End Of 48V BSG Gasoline Engine

This paper mainly analyzes and studies the forces on the crankshaft front end of a gasoline engine(1.5L)equipped with 48 V BSG(Belt-driven Start Generator)system,including the crankshaft,crankshaft bolts and damping pulley.The 48 V BSG system changes the working state of the front end of the crankshaft of the original engine,which leads to the fall off of the damping pulley during the operation of the engine.The primary analysis is that the belt pulley falls off due to the looseness and failure of the big bolt of the crankshaft.To solve this problem is a very important problem of quality assurance.This paper analyzes and studies this subject.Firstly,the mathematical model of crankshaft is introduced into EXCITE TD(Timing Drive)software to establish the power system model of BSG system.According to the boundary conditions,the system shape,load,peak force of belt and the stress at the damping pulley are calculated as the basis of the strength analysis of crankshaft front end.Secondly,the model of crankshaft front end is established by ABAQUS software according to EXCITE TD software provides boundary conditions to analyze the strength of crankshaft front fillet,strength of crankshaft big bolt and slip characteristics;then,FEMFAT software is used to analyze the fatigue strength of crankshaft fillet to obtain the fatigue safety factor;then,according to the strength analysis results,slip analysis results and fatigue analysis results of CAE software,the possible causes of the loosening failure of crankshaft big bolt and its optimization are found out Finally,the improvement effect of the optimization scheme is verified by special experiments.In this paper,we have used EXCITE TD,ABAQUS,FEMFAT,ANSA and other software to carry out the multi-body dynamics simulation calculation,and obtained the position change of the gear train under different working conditions,the slip rate of the belt and the peak load acting on the crankshaft.The results of simulation analysis show that the main reason for the looseness of damping pulley is that the existing friction contact cannot transfer torque of 180.2N·m,the maximum torque that can be transferred by local sliding is about 140N·m,and the maximum torque can be transferred without sliding is about 100N·m.The optimization suggestion is to increase the radius or friction coefficient at the fillet of bolt head;from the perspective of fatigue strength,the stress state at the fillet of crankshaft front notch is more critical than that at the fillet of crankshaft journal,the minimum safety factor at the fillet of crankshaft front end is less than 1,and the reliable safety factor should be at least 1.1 or higher.It is recommended that additional surface treatment be carried out while increasing the radius at the front corner of the crankshaft.The process and results of simulation analysis in this paper are significant for improving the design of BSG system in gasoline engine,and can also be used for reference by related parts manufacturers and research institutes.