Research On Broken Teeth Fault Of Diesel Engine Timing Gear And Shaft System Vibration Improvement

As an important part of shafting system in the diesel engine,the timing gear system is the core transmission mechanism to ensure the normal operation of the auxiliary equipment in the diesel engine.As the power density of diesel engines continues to increase,the vibration of the shafting system becomes more and more obvious.The broken tooth fault of the diesel engine timing gears frequently occurs,which seriously affects the normal operation of the auxiliary equipment.This paper takes a certain type of fault gear transmission system of marine 20V170 diesel engine as the research object,explores the vibration characteristics of diesel engine shafting,analyzes the causes of the broken gear fault of timing gear train,and optimize the vibration of the shaft.The main research contents are as follows:The semi-bending and torsional coupling model of multi-branch diesel engine with timing gear system is established according to lumped equivalent parameters.Based on the coordinate transformation principle,the model is transformed into the global coordinate system to simulate the inherent characteristics of the shafting system.The modal of the same type diesel engine shafting is carried out.The test which compared with the theoretical calculation results,verifies the accuracy of the inherent characteristics of the diesel engine shafting.Analyzing the inherent characteristics,it is found that the first-order natural frequency of the shaft is close to the working speed,and resonance is easy to occur.Through the force analysis,the principle of moment balance,the calculation principle of energy time-varying mesh stiffness and the micro-slice theory,the excitation force model of each working component of the diesel engine shaft is established.It is found that the amplitude of the excitation frequency of each type of load basically decreases with the increase of the harmonic frequency.The cylinder and camshaft excitation are medium and low frequency excitation,and the gear excitation is medium and high frequency excitation.Under the two conditions of uniform explosion pressure and uneven explosion pressure,the forced vibration characteristics of the diesel engine shaft are analyzed.It is found that the shafting vibration is intensified under the uneven explosion pressure of the cylinder.Under the two explosion pressure conditions,the fatigue strength of the three-dimensional finite element model of gear failure component is performed.Under non-uniform explosive pressure conditions,the gear will fatigue fracture.Check and analyze the cause of the broken gear tooth fault.Afterwards,predict and analyze the forced vibration of the diesel engine shaft with the broken tooth fault,characteristics of vibration response of the shafting system are increased.Through parameter sensitivity analysis,it was found that after adjusting the torsional stiffness of the oil supply camshaft,the instantaneous rotation speed fluctuation of the oil supply camshaft was reduced;the measures of thickening the tooth width and installing a torsional vibration damper at the free end of the oil supply cam were adopted.The system performs vibration improvement analysis to optimize the gear meshing environment and camshaft oil supply timeliness.The gear transmission shaft system of diesel engine established in this paper fully considers the branch shafting system and related ancillary equipment,improves the load boundary conditions of the diesel engine shafting.It can provide theoretical support for vibration response prediction,broken tooth failure analysis,and vibration improvement of a complete diesel engine shaft.