Gear Mesh Excitation Research Articles

Design of a High-Level Diagnostic System

The use of vibration signals produced by the operation of a machine to control its operations and detect developing faults is appealing because of the ruggedness of vibration sensors and their ease of placement. A diagnostic system that employs a few sensors, remotely located from a number of vibration generating mechanisms, to analyze the performance of these mechanisms is termed a “high-level” diagnostic system. The goal of such a diagnostic system is to infer from the remote vibration sensors the characteristics of the internal sources (such as forces and pressures) which could not be easily measured directly. The use of multiple sensors and advanced signal processing methods is necessary for such a system to be viable. A series of studies on vibration excitation, propagation, sensing, and signal processing that demonstrate the basic feasibility of such a diagnostic system are described. The design of a high-level diagnostic system for detecting the combustion and gear mesh excitations in a diesel engine analysis is presented, along with the results of a preliminary application of the system.

Dynamic Behavior of a Journal Bearing in a Planet Gear

The dynamic analysis of the journal bearing which supports the planets of an epicyclic gear stage is described. The analysis includes an assessment of the damping characteristics of the bearing, the stability, and the response of the planet to gear mesh interactions between the sun, the planet, and the ring gear. A digital program was developed which provides the numerical solution of the equations of motion by forward integration in time. The full nonlinear expressions have been used for both the hydrodynamic bearing forces and the gear mesh interaction forces. Centrifugal and Coriolis effects due to the planetary motion are taken into account. Numerical results for a PT6 reduction gearbox indicate that the bearing is highly stable and not adversely affected by gear mesh excitations.

Gear Mesh Excitation Spectra for Arbitrary Tooth Spacing Errors, Load and Design Contact Ratio

The tendency for gear pairs to exhibit vibration, noise and dynamic tooth loads is influenced by tooth spacing errors, load, design contact ratio and profile modifications. This paper describes an analytical method for assessing the influence of these factors on the excitation force at the gear mesh for gears with a form of profile modification which gives zero excitation at design load in the absence of spacing errors. Amplitude modulation characteristics of the excitation spectrum are of interest since this effect often results from gear manufacturing processes. Tooth spacing errors tend to spread the gear mesh excitation energy over a band. Excitation orders inherent in the gear pair without spacing errors are reduced in amplitude, and the excitation energy shows up in closely adjacent side bands if the errors are a low order nature. Random type spacing errors tend to spread the excitation energy over a broad band while reducing the inherent components except near design load. This would tend to attenuate gear noise and dynamic tooth loads associated with resonant conditions of a gear system.