Reduction of Rattle Noise of a Direct Engine-PTO Driveline of Agricultural Tractors: Part I. Measurement and Analysis of PTO Rattle Noise

Abstract

Introduction of a direct engine-PTO driveline has reduced production costs and increased power transmission efficiency. However, a severe rattle noise was generated in the PTO gearbox during idling. This study was conducted to: (1) investigate characteristics of the PTO rattle noise and to determine how much it should be reduced (Part I, this article); (2) use computer simulation to investigate the primary causes of PTO rattle noise and the effects of some driveline design parameters on PTO rattle noise (Part II, companion article); and (3) investigate reduction of PTO rattle noise by a torsional damper (Part III, companion article). The PTO rattle noise of the tractor used in this study was measured at 30 mm from the PTO shaft and analyzed in both time and frequency domains to investigate its temporal and spectral characteristics. The loudest PTO rattle noise was 102 dBA at the PTO shaft and occurred at an engine idle speed of 880 rpm with the PTO gear in neutral. The sound pressure of the noise varied periodically with the same period of the engine expansion strokes. Its frequency bandwidth was as wide as from 0.5 to 10.0 kHz, and the peak sound pressure occurred at frequencies of 3.6, 6.5, and 7.8 kHz, which corresponded to the natural frequencies of the driven gear in the PTO gearbox. The engine speed did not affect the spectral characteristics of the PTO rattle noise. The PTO rattle noise of the tractor used in this study was at least 7 dBA higher on average than those of the imported tractors having the same type of PTO driveline. This meant that the PTO rattle noise of the direct engine-PTO driveline in this study must be reduced by at least 7 dBA.