Replacing a conventional automatic transmission with a high torque capacity, full-toroidal traction drive Infinitely Variable Transmission (IVT), delivers fuel economy benefits approaching those achieved by hybrid drivelines when a suitable balance between battery life and fuel economy is implemented, but with minimal additional on-cost, weight and complexity. These benefits are achieved by optimizing the engine operating conditions, eliminating the torque converter and removing torque interruptions during the gearshifts.
Recent application of a non-optimal IVT to an Optare Solo bus (an 11,300kg European Midi-Bus) produced fuel savings of 19% over the standard Allison 5-speed automatic transmission. These measurements were independently performed by the internationally recognized Millbrook Proving Ground, UK. The precise control of the engine operating condition was demonstrated and this, in conjunction with the ability to decouple engine speed from wheel speed provides new opportunities to engine designers.
This paper describes the operation of the IVT and the fuel economy benefits achieved in an Optare Solo European Midi-Bus application. Extending the IVT to satisfy larger commercial vehicles by creating a modular family of transmissions is discussed, together with the future hybridization potential of the IVT