Application Research On Engine Manufacturing Accuracy Based On Consistency Of Friction Loss

The rapid development of China economy in recent decades has led to the rapid expansion of the automobile industry.As the traditional power source of the automobile,the production of the engine has been increasing year by year.As the power core of the automobile,the process of engine manufacturing has the characteristics of complex process and high precision requirement.However,due to the lack of scientific basis,the dimension tolerance distribution in the design process is based on experience.Which lead to the problems of significant variation of engine performance & quality,lower reliability and poor durability.It also creates huge problems when matched with other products.The friction loss of the engine is one of the most important indexes for evaluating engine performance,and also has a direct impact on the performance of engine torque output and fuel consumption.This paper aims to improve the consistency of engine friction.The influence of tolerance on the variation of engine friction is studied.In order to get more scientific and reasonable tolerance and reduce the variation of the engine friction loss,the manufacturing capacity of the dimension is also studied.Based on the elastic fluid lubrication(EHD)theory,the friction loss simulation model of the crankshaft system and the piston system is established for a 1.2L engine.The simulation model is calibrated and verified according to the experimental results of engine bench.Based on the simulation model established,the influence of the dimensional tolerance and geometric tolerance on the friction loss of the crankshaft system and the piston system is analyzed respectively.The trend of the friction loss change caused by the dimension is studied,and the influence of tolerance on friction loss variation is also studied.The critical dimensions of the friction loss of crankshaft system and piston system are obtained.Based on the critical dimensions obtained,the relationship model of the critical tolerance and friction variation is established through the kriging interpolation theory.With the consideration of the manufacturing capacity of the existing production system,the tolerance of critical dimensions is optimizedThe results show that,compared with the original tolerance design,the friction variation of crankshaft system decreases by 44.67% and friction variation of piston system decreases by 33.91%.The study provides a scientific basis for the allocation of tolerance.