Error Analysis And Precision Control On Crank Radius Of Crankshaft

As one of the six key parts of engine,the crankshaft's main function is to convert the force coming from the connecting rod into torque,and pass its output to other accessories,so as to drive the engine.The fluctuation of crank radiuses,one of the key size,affect the engine's compression ratio.Therefore,it is necessary to decrease the fluctuation of crank radius and improve the crankshaft manufacture precision and then improving the performance of engine.This paper selects a type crankshaft model as the research object,and analyzes the effect of craft system error on the machining accuracy of crank radius using the actual production data.Then the main error sources are identified.The research includes the following three aspects:Firstly,the crankshaft grinding process system is analysed,combined with the characteristics of the actual machining crankshaft,and the tangency of external cylindrical grinding and non-circular servo track of grinding is obtained,and the grinding process is knowed well.Then the factors that may affect processing precision in the process system through the analysis of the crankshaft grinding is also expolored.At the same time,the influence factors of the possibility one by one combining the actual characteristics of crankshaft machining and present processing situation is analyzed.Finally,the two main reasons that influence radius size precision of the crankshaft are founed.One important factor is the crankshaft stress deformation caused by the error of crankshaft,the other is datum error.Secondly,the crank radius error caused by the deformation of the crankshaft stress is studied.Combined with the stress analysis of the crankshaft and the clamping positioning way during grinding process,the elastic deformation of the crankshaft journal axis under different phases is obtained through the finite element simulation method.According to the movement relationship between the grinding wheel and crankshaft and the deformation law under different crank shaft angle,an error analysis model of the crank radius based on the theory of grinding trajectory reconstruction is established;And the main factors influencing the crank radius difference between cylinders under the crankshaft stress are determined through the analysis of different power for the crank radius: grinding force and tip pressure.Then the correctness of the crankshaft finite element model and the error analysis model of the crank radius through the experiment are verified.Finally,the crankshaft and datum error are studied.Combining crankshaft clamping positioning way,comprehensive analysis is carried on aiming at factors that may affect the machining accuracy of the crankshaft in the process of grinding,,and the main factors affecting the crank radius difference between cylinders to be fixture positioning device error are determined.Axial clamp coordinate system and the error analysis model are presented,and the influence of the positioning element error for the crank radius is calculated.At last the correctness of axial clamp coordinate system and the error analysis model through experiment are verified.This paper explores the key factors that affect the crankshaft machining accuracy in the process system and get the crankshaft axis force elastic deformation law under different phase and reconstructs the cutting theory trajectory of crankshaft grinding and designs the error analysis model of crankshaft crank radius and improves the influence of the crankshaft fixture and benchmark for machining accuracy and leads to the building method of axial fixture coordinate system.All of these can improve the crankshaft manufacture precision and engine performance.