Midi-Bus Infinitely Variable Transmission Retarder Deletion Study

A typical 10 tonne Midi-bus driveline includes an electric retarder device, located at the transmission output, which is used during vehicle braking thereby reducing service brake usage and wear. The retarder is activated via the brake pedal and operates down to speeds of 1 kph.

To reduce cost and complexity it may be possible to delete the electric retarder when an infinitely variable transmission (IVT) powertrain is used in place of the standard 5 speed automatic transmission (5AT). The purpose of this study is to determine the amount of service brake usage, in terms of energy dissipation, for both the 5AT (with retarder) and IVT (without retarder) over the Millbrook London Transport Bus (MLTB) drive cycle. Validated MATLAB^® dynamic models of both drivelines are used to calculate retarder and service brake usage.