Abstract
A continuously variable transmission (CVT) that maintains the engine in its optimum power range has the potential to solve two issues of fuel economy and tail-pipe emissions. In 1999, a traction-drive half-toroidal CVT was commercialized for a large-displacement engine in front-engine rear-drive vehicle. In this paper, experiments on a prototype confirmed the possibility of a six-power-roller variator developed for the purpose of further increasing transmission torque capacity up to 430 Nm as opposed to a current four-power-roller, and further simplifying the speed-ratio control system. Technical advancements include: confirmation of synchronization and stability of six power rollers; establishment of a cost-effective speed-ratio control system using a small three-port electro-hydraulic pressure proportional valve; replacement of the hydro-mechanical servomechanism with a simplified sensorless control system.
Keywords:Power transmission, traction drive, CVT, speed-ratio control, efficiency, synchronization, pressure proportional valve, six power-roller