Reduction of Driveline Boom and Vibration of 40 seat Bus through Structural Optimization

Paper #:
  • 2017-28-1926

  • 2017-07-10
NVH plays key role in customer perception of vehicle quality. In today’s market scenario,NVH is one of the major deciding factors of vehicle acceptance like fuel efficiency. An NVH problem is identified and analyzed on a recently developed M2 category bus platform and suitable diagnosis is presented in this paper. Severe vibration is experienced on the bus floor predominantly towards rear part of bus. Vibration occurs prominently in 4th gear wide open throttle operating condition between 1300-1600 engine RPM. This phenomenon is also accompanied by an acoustic boom in the passengercabin during the afore mentioned RPM zone. This paper explores the possibility of reducing NVHlevels by working on the transfer path with minimum modification on power-train. The task was to identify the source of the vibration and the transfer path to the target locations. Baseline NVH measurements revealed the problematic rpm zone and related frequencies. Preliminary torsional measurements conducted on powertrain indicated hightorsional excitation to the driveline in the identified RPM zone. Further, Operational DeflectionShape (ODS) analysis revealed that the transfer path to the cabin is rear differential unit andsuspension links. The dominant frequencies were identified along the transfer path and suitable modifications were made on the identified locations. A reduction of 50% in floor vibration level and 3dB(A) reduction in cabin noise level accompanied with improvement in loudness by 4 sones is achieved. These modifications were found to be suitable for future vehicle architecture changes based on power and torque requirements.
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