Improving vehicle dynamics and fuel economy with an E-four hybrid powertrain

Toyota Motor Corporation developed the Toyota Hybrid System with CVT (THS-C) for the Toyota Estimaminivan. The THS-C is based on Toyota’s Super CVT (K110), where the conventional torque converter is replaced by a torsional damper and a newly developed motor/generator. For smooth switching between the different driving modes it makes use of wet multiple disc clutches and a planetary gearset arrangement. The Toyota Estima is also equipped with a motor/generator which directly drives or brakes the rear wheels for optimal vehicle dynamics and fuel economy. This feature will also be installed in the new hybrid Lexus RX400h, which is driven by an up-scaled version of the Prius powertrain. The powertrains in the mentioned vehicles are in fact an E-Four full hybrids with separate electric motors on front and rear axles. The first goal of this paper is to model the E-four of the Estima in ADVANCE; a coupled vehicle dynamics and powertrain simulation program developed by TNO Automotive. The second goal is to perform simulations with this software and evaluate the results. The results will be used to validate the THS-C as a technology carrier for ongoing and new research on integrated powertrain control and pulley CVTs for hybrids.