Study on interactions between tooth backlash and journal bearing clearance nonlinearity in spur gear pair system

Gear transmissions with journal bearings are widely used in power machinery. The existences of the large bearing clearances and backlash lead to variations of tooth contact status under different operation conditions and assembly states (bearing center distance). The purpose of this paper is to examine the dynamic response of the spur gear-pair system and interactions between bearing clearance and the backlash. In the system dynamic model, the contact force on backside and journal bearing forces, where both clockwise and anticlockwise rotation of the gears exist, are considered simultaneously. Shift of the bearing position is also taken into account. In quasi-static analyses, equilibrium positions of shaft journals in bearing clearance are figured out by Newton iterations in a wide range of rotational speeds and input torques. In dynamic analyses, vibration responses are presented by frequency-amplitude curves, spectra, bifurcation and orbits, where oil whirl and tooth separation are observed. Finally, tooth wedging phenomena led by shift of bearing position are presented. The results show that the bearing clearances provide self-adaptive characteristics, both the shortening of bearings center distance and the input torque contribute to the occurrence of the tooth wedging.