NVH Improvement of the BEV Transmission by Altering Bearing Mounting Arrangement

<div class="section abstract"><div class="htmlview paragraph">As per metaphor, “The squeaky wheel gets the grease,” and in the case of Battery Electric Vehicles (BEVs), the transmission system has become the focal point for NVH (Noise, Vibration, and Harshness) improvements. With the engine being replaced by the near-silent electric motor, the noise generated by the transmission has become more prominent, demanding greater attention to noise reduction. This shift has created a pressing need for innovations in both design and manufacturing processes to enhance the overall quietness of the vehicle. As a result, ongoing advancements are being made to address and improve the NVH characteristics of BEV transmissions.</div><div class="htmlview paragraph">Following paper will discuss the improvement in NVH achieved through a design innovation in the way bearings are installed and demonstrated a significant amount of improvement. We have used SMT MASTA as a simulation tool to predict the expected results and a Transmission Dyno test bench in an anechoic chamber to test the NVH performance on physical sample. The innovation was done on a small single speed two stage reduction gearbox coupled with a 100 Nm, 14000 RPM battery electric motor.</div><div class="htmlview paragraph">While bearings may seem to have a minor influence on overall NVH, their role in transmitting reaction forces to the housing is critical. By innovatively altering this transmission mechanism, we’ve significantly reduced transmission error (TE), gear misalignment, and vibrations, as predicted by advanced gear simulation tools like MASTA. Rigorous testing of the prototype in an anechoic chamber confirmed these predictions, resulting in a notable 2 to 6 dB(A) reduction in NVH.</div><div class="htmlview paragraph">Additionally, this innovative bearing arrangement optimizes bearing wear and extends the overall duty cycle. By redistributing axial and radial forces, we’ve achieved a 25% reduction in damage for a given duty cycle, or equivalently, a significant increase in lifespan while maintaining the original performance level.</div></div>