Influences on the lubricant supply of grease lubricated gears

Abstract

Greases have a variety of advantages when special operating conditions apply. Mainly related to large, slow-running gear drives such as used in heavy industry applications, grease lubrication can also be the preferred solution for small, fast running gear drives. Conse-quently, the calculation of the wear service life within the gear design process is essential. Due to their flowing properties, there is a danger of losing the lubrication supply depending on the operating conditions, boundary conditions and grease properties. While a circulating lubricant ensures a continuous lubricant supply to the gear mesh, channeling includes the risk of starved lubrication and consequentially, even a discontinuation of the lubricating film that can lead to heavy damages of the gearbox. The experimental investigations on a modified FZG back-to-back test rig show a strong effect of operating conditions and grease properties on the lubricant supply: A higher amount of grease in the gearbox and a higher lubricant temperature support circulating, whereas, a higher consistency of the grease supports channeling. Based on the results, a first calculation approach is developed that approximates the lubricant supply of grease lubricated gears for the gear design process.

Extended Wear Lifetime Calculation for Grease Lubricated Gears in Consideration of Surface Hardness and Roughness

“…However, the results of this study confirm the course of the wear curve for grease lubricated gears acc. to Plewe [4], as long as they are ini sufficient lubricating conditions (see [8,17]). The wear coefficients of the through-hardened wheels show for the first speed stage vt1 clearly higher values compared to the case-hardened pairing.…”