Axle & PTU Gearset NVH
The ring & pinion gearsets (spiral bevel) of front and rear drive axle modules (independently-suspended & full-beam) as well as many PTUs, are particularly challenging from a manufacturing quality standpoint. As a result, they can often be significant contributors to the tonal noise heard in-vehicle and associated warranty claim issues. Consequently, it is now commonplace for the majority of axle assemblies to be 100% tested at the end-of-line, either within assembled axles (with or without tubes and/or with/without driveshafts), or within carrier (centre-section) units.
The rigid, "lumped-mass" nature of many axle centre-sections means that a significant proportion of the "NVH-energy" is shaft-borne (as opposed to radiated noise emanating from casing vibration). As a result, many successful ABD-equipped axle test systems worldwide are configured to measure shaft-borne:
■ torsional acceleration, and/or
■ dynamic torque (torque fluctuation, or "ripple")
often in addition to linear casing vibration (measured using contact accelerometers and/or non-contacting laser vibrometers).
ABD offers two main NVH measurement & analysis systems for axles: Plato and Elsa.
