Experimental investigations about the influence of oil lubricant between teeth on the gear rattle phenomenon

The article describes an experimental investigation into the "gear rattle" phenomenon in automotive manual transmissions with a special focus on the influence that lubricant oil may have in reducing this undesirable event. The experimental analysis has been conducted in order to validate a theoretical model developed by the authors that accounts for the presence of oil between the meshing gear teeth of unloaded gear pairs during the no-contact phase. An original measurement technique has been adopted for the tests that consists of the acquisition of the angular relative motion of a gear pair by two high resolution encoders. The experimental test rig designed for this analysis offers the possibility of varying the distance between the wheel axes so that the influence of the backlash variation on the rattle phenomenon can be investigated. The paper presents the results of a series of experiments conducted on helical gear pairs from an automotive gear box in the "idle gear rattle" condition by varying the lubrication mechanism. The experimental results show good agreement with the expectations provided by the theoretical model.