Toyota new driveline design for FR passenger vehicle

Paper #:
  • 2017-01-1130

Published:
  • 2017-03-28
Abstract:
Renewed platform of upcoming flagship FR vehicle demands high levels of driving performance, fuel efficiency and noise-vibration performance. The newly developed driveline system must balance these conflicting performance attributes by adopting new technologies. This article focuses on several technologies that were needed in order to meet the demand for noise-vibration performance and fuel efficiency. For noise-vibration performance, this article will focus on propeller shaft booming noise. This noise level is determined by propeller shaft’s excitation force and sensitivity of differential mounting system. In regards to propeller shaft’s excitation force, the contribution of axial excitation force was clarified. This excitation force was decreased by adopting a double offset joint(DOJ) as propeller shaft’s second joint and low stiffness rubber couplings as first and third joint. The input to the body and its sensitivity were decreased by separating the pitching resonance of body mount bushings and differential mount bushings. For improving fuel efficiency, differential gear (diff) efficiency improvement is described in this article. Hypoid gear specifications, bearings, and oil lubrication system were optimized to improve fuel efficiency. Thus, new diff efficiency is superior to the previous model in spite of the bigger size and it achieves its target. Low pinion offset, and low spiral angle of the hypoid gears enable meshing loss reduction. Adoption of ball bearings for drive pinion axis further enables the reduction in losses compared to conventional taper bearings. Optimization of the carrier lubrication structure and low oil level enable additional reduction in losses, and improve the life of ball bearings by limiting excessive oil supply to the bearings.
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