Non-Linear Dynamic Modeling And Control Of Vibration And Noise Of Idle Gear

Gear is an important and general part to connect rolling parts and transmit power,and it is applied widely in mechanical equipment of manufacture,agriculture,national defense,aerospace,transportation and other industries.In the auto industry,idle gears are important parts of timing gear system of the internal combustion engine.The idle gear is subjected to high speed and fluctuant load,and it rotates freely with the fixed shaft on the surface of bearings,which make it easily generates rattle within the limits of gear clearance and influences the riding comfort and durability,even causes earlier fatigue failure of some parts.Also,rattling noise impacts the comfort degree of drivers and passengers.For this reason,studying the non-linear dynamic mechanism of idle gear rattle is important for preventing earlier failure of timing gear system and controlling automotive vibration and noise,which has important theoretical significances and engineering application value.The paper aims at idle gear rattle problems,presenting dynamic models of the idle gear with unbalance mass and the idle gear with journal deflection,and the influences on idle gear by the mass eccentric distance,backlash and journal deflection distance are analyzed.O n the other hand,the control method s of vibration and noise of idle gear are presented,and the effect of vibratio n and noise reduction by tooth profile modification is calculated theoretically and analyzed experimentally.The main work carried out as follows:(1)The mechanism of the idle gear impact,journal deflection and the vibration and noise of the idle gear are introduced.The non-linear working mechanism of idle gear and the cause of rattle noise are studied.These work provide some prerequisites for non-Linear dynamic modeling of idle gear.(2)For the problem of less non-linear factors in recent gear rattle dynamics,a time-varying and asymmetric mesh stiffness is considered,and a dynamic model of the idle gear with unbalance mass is proposed to analyze the influence on the gear system by the time-varying centrifugal force and inertia force.Also,the impact on the dynamic transmission error and structure noise of idle gear with different mass eccentric distances and backlashes is studied.This work lays a strong theory foundation for the study of idle gear with unbalance mass.(3)Considering the time-varying oil film stiffness of journal deflection,a dynamic model of the idle gear with journal deflection is established and the calculation method of time-varying center distance,pressure angle,contact ratio and backlash are proposed.Also,the impact on the dynamic transmission error and structure noise of idle gear with different distances of journal deflection is studied.This work lays a strong theory foundation for the study of idle gear with journal deflection.(4)For reducing the vibration and noise of idle gear,the control method of unbalance mass and journal deflection and the method of tooth profile modification are presented.A calculation model of the mesh stiffness of the gear pair in single and double tooth engagement with tooth profile modification is proposed.Also,the impact on the dynamic transmission error and structure noise of idle gear with the different amounts and lengths of profile modification is studied,and the effect of vibration and noise reduction by tooth profile modification is verified by rolling gear experiment before and after profile modification.