Tech Lic. ISRN LUTMDN/TMME--1013--SE. Lund 1997

Abstract:

In this report a model for calculations of external spur gear dynamics has been presented which takes into account factors such as contact away from the theoretical line of action, elasticity coupling between the teeth, bearing deformations, tip relief and outer system. The contact positions and force levers are determined by the use of the undeformed gear geometry, the gear wheel stiffness is calculated using a finite element method program and contact deformations are taken into account.

The model presented has been used for studying a specific transmission set. The gear ratio is equal to one and the bearings are stiff. In this study it has been shown that it is necessary to take into account contact away from the theoretical line of action, elasticity coupling and outer system if accurate results are to be obtained.

The parametric resonances due to parameter variations in the equations of motion have been studies for the transmission set. The difference between a dynamic factor based on the maximum contact force or one based on the maximum tensile fillet stress have been studied and it has been shown that a conservative design is generally made for the transmission set if a factor based on the maximum contact force is used. It has been observed that if the maximum static tensile fillet stress is constant when comparing gear sets with different gear modules small modules cause greater gear dynamics. This is especially evident at the resonance speeds. It has also been shown that the magnitudes and positions of the resonance peaks vary in the frequency plane with respect to different amount of driving torques. This effect cannot be studied when models that so not take contact away from the theoretical line of action into account are used. It has been shown that choice of tip relief magnitude is not only decided with respect to the amount of driving torque but also speed of revolutions, and a too great magnitude of tip relief increases the dynamic effects. A mass optimization for the studied transmission set has done and it has been shown that the transmission set cannot be optimized with respect to tensile fillet stresses, contact stresses and transmission error at the same time.