Nakade, Y., Kamada, A., Ueno, K., Kume, M. et al., "Shift-by-Wire System for Lexus RWD Vehicles," SAE Int. J. Engines 10(2):689-694, 2017, doi:10.4271/2017-01-1094.
Shift selection devices are desired to be flexible for design and layout, in order to realize the next generation of cockpits for Lexus vehicles. In addition, refined shift operation feelings are also required to be suitable for Lexus vehicles. To meet these demands, the Lexus LC500 has been equipped with a shift-by-wire system, which replaces the mechanical linkage between the shift selector and transmission with electrical signals and an actuator. This shift-by-wire system will be installed in a wide variety of Lexus powertrain lineup, including conventional gas vehicles and hybrid vehicles. Therefore, the next generation shift-by-wire system for Lexus has been developed with high reliability and applicability. This technology will be essential when autonomous driving and autonomous parking systems are realized in the near future. To enable shifting of the parking mechanism in a simple configuration regardless of the engine operation state, shifting of the parking mechanism is performed by an add-on electric parking actuator, and shifting the driving force direction is performed by a transmission control unit in each powertrain system. The shift selection method basically follows an “h” pattern shift lever and a push-type parking switch, which Toyota has used in hybrid vehicles for many years. Additionally, emotional shift selection devices are even more in tune with the driver’s senses. The new flat type high-output parking actuator is developed to enable adoption of this system in rear-wheel drive (RWD) vehicles. This application has a difficult installation environment in terms of space and heat between the transmission and the floor tunnel, and also requires large torque to shift the parking mechanism because of the comparatively high vehicle weight. This paper outlines the new system and its major technologies.