AGMA 15FTM23 PDF

With the current trend towards Electric Vehicles (EVs), there is likely to be increasing focus on the noise impact of the gearing required for the transmission of power from the electric motor (high speed) to the road. Current automotive Noise, Vibration and Harshness (NVH) understanding and methodologies for total in-vehicle noise presuppose relatively large Internal Combustion (IC) contributions compared to gear noise. Further, it may be advantageous to run the electric motors at significantly higher rotational speed than conventional automotive IC engines putting the gear trains into higher speed ranges. Thus, the move to EV or Hybrid Electric Vehicles (HEV) places greater or different demands on gear train noise.

This work combines both a traditional NVH approach (in-vehicle and rig noise, waterfall plots, Campbell diagrams, and Fourier analysis)—with highly detailed transmission error measurement and simulation of the complete drivetrain—to fully understand noise sources within an EV hub drive.

The transmission error testing has been performed on both the full assembly with the three-stage gear train and on individual gear pairs using a dedicated transmission error measurement rig. Highly accurate rotary encoders are used to measure transmission error through different stages of the gear train in order to identify sources of excitation.

For comparison, a full Computer-Aided Engineering (CAE) model has been built, which includes the flexibilities of all components, gears, shafts, bearings, and casing. Standard analysis is used to simulate the system deflection under input loads with corresponding gear misalignments, contact patches, and transmission errors. Contact patches are compared to tooth marking test results. Further, a novel advanced calculation is performed which iteratively couples deflections of the full system model with detailed tooth contact analysis at the gear meshes. This analysis shows how the gear meshes and the deflections of the full transmission change through the gear meshing cycles. This analysis can include detailed, measured, manufactured gear geometry, and various tolerances and errors within the system and calculate both the associated individual mesh and system transmission errors and their harmonic content.

Detailed test and simulation identifies the noise sources to be the meshes of the three gear sets and captures a full understanding of them. Methods are presented to accurately derive and compare the individual gear mesh transmission errors from test and simulation of the complete unit. Further analysis of the individual results indicates both gear design and manufacturing considerations to be optimized to reduce noise. The results of prototype testing of design changes are given showing significant in-vehicle noise reductions.

A detailed methodology is presented, combining both a full series of tests and advanced simulation to troubleshoot and optimize an EV hub drive for noise reduction.