Measurement of the operating vibration mode shape of helical gears

Helical gears vibrate in rotational, axial, transverse and tilting directions due to the helix angle. Among them, the rotational vibration was reduced considerably by the better dimension design and proper flank modification. As the result, other noise resonance peaks due to the axial, transverse and tilting vibrations have become more noticeable. For further noise reduction, it is important to clarify the physical mechanism of each resonance peak by actual measurement. In this paper, a method is examined to measure the operating mode shape of each vibration resonance peak by directly putting the acceleration pickups on the rotating gear shaft and taking out the signal through slip ring. The three-dimensional (rotational, axial, transverse and tilting) vibrations of rotating helical gear shafts, three-directional (X, Y, Z) vibrations of bearing holders and the radiated gear noise are measured at same time. As the result, the operating mode shape and animation of each vibration resonance peak are obtained based on the measured real-time vibration waveforms of rotating gear shafts. The physical mechanisms of principal rotational, axial, transverse and tilting vibration resonance peaks are clarified. In particular, several new interesting vibration modes are found: the synchronous transverse vibration of drive and driven gear shafts is in parallel with the line of action (LOA), but the individual transverse vibration of drive or driven gear shaft is perpendicular to the LOA.