Coupling Researches On Tribological And Dynamical Behaviors Of The Crankshaft-Bearing System Of Internal Combustion Engines

Crankshaft bearing system is one of the most important components in Internal Combustion Engines (ICE). The performances of the crankshaft bearing system not only have direct effect on the reliability and durability of the engine, but also restrict the development of the engine potentiality. As a result of the complicated structure and loading conditions, it is hard to understand or analyze the coupling tribological and dynamical behaviors of the crankshaft bearing system. The tribological and dynamical behaviors have to been studied independently on the domain of tribology or dynamic over a long period of time. Therefore, to study the behaviors of the crankshaft bearing system coupling bearing tribology with crankshaft dynamics is very important both in theoretical and practical sense.At the beginning of this dissertation, the present status of the tribological analysis of ICE journal bearings, dynamical calculation of crankshaft and correlative researches of rotor dynamics are reviewed. To reveal the relationships between tribological and dynamical behaviors of shaft bearing system, an analytical model of the shaft bearing system is brought forward. According to the model, the shaft bearing system is taken as an auto-control system, and the bearings and shaft are taken as controllers and controlled object. The analytical model has a clear physic sense and can be applied to nearly all the types of shaft bearing system.According to the analytical model, a new coupling analyzing method for shaft bearing system is put forward. With this method, a simulating model of the shaft bearing system is set up at first. Then the simulation model is analyzed by the joint simulation of ADAMS and MATLAB. This method provides an effective tool to analyze the coupling tribological and dynamical behaviors of complicated shaft bearing systems.By using the new coupling analyzing method, the tribological and dynamical behaviors of rigid shaft bearing system exciting with impact, sine and rotating loads are studied. The frequency response of shaft bearing system is evaluated with frequency-sweeping method. It is shown that the resonance frequency of the shaft bearing system has relation with the shaft rotating speed, bearing clearance, lubricant viscosity. The influences of rotating speed of shaft, width and clearance of bearing, lubricant viscosity on the behaviors of shaft bearing system are discussed.Based on the theory of flexible multi-body dynamics, a simulating model of flexible shaft bearing is set up. By the joint simulation of ADAMS and MATLAB, the flexible shaft-bearing system is analyzed. The coupling tribological and dynamical behaviors are compared between flexible and rigid shaft bearing systems.Experiments of flexible shaft-bearing system are done on the test set designed by the author. A non-contact electromagnetic actuator is used in the experiments. The results of the experiments are introduced and discussed. The influences of rotational speeds of the shaft, length and clearance of the bearing on the vibration amplitude of the journal center are analyzed. It is shown that the experimental results are coincident with the theoretical analysis.The crankshaft bearing system of N485 diesel engine is analyzed with the method presented above.The coupling simulation model of crankshaft bearing system is built with the finite element model of crankshaft. The tribological behaviors of main bearings and the three dimension vibrations of the crankshaft are discussed in detail. It is shown that the coupling method is efficient to analyze the tribological and dynamical behaviors of crankshaft bearing system.