Integration of Independent Front Axles for Gear Mesh Energy

The need for improved axle NVH integration has increased significantly in recent years with industry trends toward full-time and automatic four wheel drive (4wd) systems. Along with seamless 4wd operation, quiet performance has become a universal expectation. Axle gear-mesh noise can be transmitted to the vehicle passenger compartment through airborne paths (not discussed in this paper) and structure-borne paths (the focus of this paper.) A variety of mounting configurations are used in an attempt to provide improved axle isolation and reduce structure-borne transmission of gear-mesh noise.

The configuration discussed in this paper is a 4-point vertical mount design for an Independent Front Drive Axle (IFDA). A significant benefit of this configuration is improved isolation in the range of drive torques where axle-related NVH issues typically exist. Much consideration needs to be given to the structure borne noise path from the source of the meshing gears to the resulting sound pressure in the vehicle. Additionally, the benefit of improved isolation can be lost if production tolerance accumulation effects and resulting mount preloads are not accounted for in the design.

This paper discusses experimental and analytical processes including Design for Six Sigma (DFSS), Variation Simulation Modeling (VSM) and Finite Element Analysis (FEA) used to study the gear mesh energy path under various operating conditions and production variations.