F2010C095
Gear Rattle Modelling and Meshing Gear Teeth Behaviour Estimation Considering Lubrication Influence
Over the past twenty years, overall vehicle refinement levels have improved significantly. At the same time, customer expectations in this area have increased, particularly as the demand for premium vehicles has grown in many market segments. This has resulted in a situation where previously disregarded sources of noise and vibration in vehicles have become more important. At idle, the lack of road and wind noise and relatively low power train noise can result in any noise source having a disproportionate effect on the occupant perception of vehicle refinement. Transmission gear rattle is one such phenomenon, the effect of which is compounded by its non-linear, potentially irregular nature. Typically, gear rattle noise is excited by engine torque fluctuations, and lubricant has damping effect on rattle. Many of the factors that can influence gear rattle are themselves complex phenomena, dependent on both the macro- and micro-geometry of the power transmission system. Reducing torque excitation from the engine is one of means for gear rattle noise reduction, but it typically requires the addition of an expensive dual mass flywheel. Lubricant behaves as a damping element for system and teeth contact in gear rattle phenomena. It is known empirically that lubricant viscosity is critical at the gear rattle threshold. This paper describes a rattle model which can predict the phenomena and analyse the contribution of gearbox design parameters, in order to minimise gear rattle noise. The model contains a gearbox model with a parameter data base, which helps quicker and consistent modelling. A gear rattle model is automatically generated and includes bearing, clutch, gear, housing and shaft components, and can include the effects of micro-geometry modifications made at the individual gear tooth level. This system model takes account of the effects of static loading on clearances and misalignments, enabling non-linear behaviour such as gear rattle to be modelled in the time domain. The direct cause of gear rattle is loose contact between meshing gear teeth in unloaded gear pairs. A backlash model is used to describe this mechanism. A gearbox was tested with a fluctuating torque excitation and measurements taken for model correlation including lubrication influence. Gear meshing behaviour was estimated from the measured speed and acceleration. The result shows that the model predicts the behaviour seen in the tests. Some measures to indicate the intensity of gear rattle can be derived from the model application and are also presented.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Testing and Simulation of Vehicle and Component Dynamics