Tuma J.

Noise and vibration problems in gearing are mainly concerned with the smoothness of the drive. The teeth contact stiffness is not a constant but it is oscillating in synchronism with tooth meshing frequency due to the oscillation of the number of tooth pairs in contact and moving the teeth contact point along the tooth flank. The oscillation of the tooth contact stiffness causes the self excited angular vibration of the driven gear. A dynamic force acting between meshing gears results in the time varying force acting on the shaft support, which excites the vibration of the gearbox housing and consequently noise. Solving gearbox noise problems at the very source is based on gear angular vibration analysis. The parameter that is employed to drive smoothness is the Transmission Error (TE). This parameter can be expressed as a linear displacement at a base circle radius defined by the difference of the output gear’s position from where it would be if the gear teeth were perfect and infinitely stiff. This paper deals with the dynamic TE measurements of a simple gear set at gearbox operational conditions that means under load and during rotation. The analysis method is focused on the processing of impulse signals generated by incremental rotary encoders attached to both the gears in mesh. The measurement technique benefits from demodulation of phase-modulated signals using the Hilbert transform. Various signal processing methods for phase demodulation are analyzed. The theory is illustrated by experiments with TE measurements on car and truck gearboxes. The relationship between the gear angular vibration and gearbox housing linear vibration is presented additionally to TE measurements. To verify experimental results the incremental rotary encoder accuracy is tested.