Stiffness Evaluation and Vibration in a Tractor Gear

The problem of gear noise in vehicles has been intensively studied in the past; however, recently the interest about this problem grew because of great restrictions in the laws regarding noise level and the increase of international competition. One of the most important vibration and noise sources is transmission error that excites the gearbox as a dynamic system, the gearbox surfaces, and connected components; the external box radiates noise. However, the current understanding of gear vibration remains incomplete, even though there is general agreement about the nature of the phenomenon. Vibrations are due to several sources: torsion resonance, impulsive or cyclic fluctuations in drive torque, gear mesh transmission error, local component vibration responses and fluctuations in the output torque demand. The concept of a vibrating system made of two gears is generally modeled through two wheels linked by the teeth mesh stiffness. In its simplest form, this model can simulate the classical linear resonance, i.e. the resonant frequency of the system. However, more complex phenomena such as parametric instabilities can be an important source of noise. In the present paper vibration problems in the gears of an industrial vehicle are investigated through the use of perturbation technique. A suitable software has been developed to generate the gear profiles in order to evaluate global mesh stiffness using finite element analysis.