Design of a planetary gear transmission for a hybrid bus

Abstract

Hybrids vehicles have a long history and a promising future and Belgium is part of it. They have a very large variety of architectures and technical options. Each one with very different results depending not only the physical disposition but also the energy management policy. The characteristics of different architectures and its specificities have been studied in this work, focusing in the series-parallel configuration known as AutoMixte. Buses, as a particular kind of vehicle, have specific requirements. The utilization of hybrid powertrains in buses is a very interesting way to reduce the pollution and the congestion in the cities at the same time, with very low investments in infrastructure and reducing the fuel consumption and the fuel-dependency of the town. Planetary gears are widely used in vehicles. In addition to the differential gear, they are one of the main components of automatic gearboxes, accumulating key advantages like longer life span and higher compactness for relatively higher ratios. The design established the optimum speed ratio as an adaptation of the speed range of the power machines to the bus speed range. The complete design respected particular compatibility rules and verified the loaded resistance using commercial software and classic formulas from international standards. The integration of the planetary gears was modelled in a global system model with all the powertrain elements in order to obtain the total maximum mechanical output of the bus. The verification of the performance of the vehicle includes a gradeability and an acceleration simulation. This work ends with the simulation of the consumption of this powertrain in the bus assuming one particular energy management policy and the standardised test for buses know as SORT. The efficiencies of the electrical machines were taken into account as well as the charging and discharging efficiencies of the battery. Specific consumption maps of the engine were used to calculate the fuel consumption of the bus.