With the increasing importance of electric and hybrid drives potentially ensue also new possibilities for the utilisation of the energy released during braking. This energy is today primarily converted by friction and is only available for further energy use in the vehicle in the form of heat. This article considers the concepts from actual electric and hybrid vehicles. Possibilities for energy saving are shown based on the drive train energy usage in different vehicle durability tests through the configuration of the brake system. These range from reducing weight, avoiding off brake drag, to regenerative braking with the reuse of the otherwise lost energy. The thermal cycling of the brake during mixed usage (regenerative and frictional braking) is presented via a simulation model. The braking energy distribution in the respective driving conditions is quantified. The consequence of the different operating conditions for the friction pair are presented and discussed in the following paragraphs: 1. Energy usage in actual vehicle operation today. 2. Influence possibilities via the brake system. 3. Kinetic energy recovery systems (KERS). 4. Driving and load conditions. 5. Influence and consequences on the friction brake. 6. Demands on the development of the friction couple. A conclusion is leading into two options for adaption of either the brake system or the friction couple to achieve a maximum overall benefit. Regenerative brakes in current electric and hybrid cars are not designed to replace friction braking. In contrary, to secure safety in emergency situations and to provide the shortest stopping distances, the friction brakes are the only reliable solution today. Even if friction pads for electric and hybrid cars have now been on road vehicles for more than a decade, no change of the basic friction brake has been visible. But with growing quantities of electric and hybrid cars on the market and having solved today's problems of energy transformation, onboard storage and brake blending, brake systems with optimised friction pads will be requested to respond to the changing operating conditions of friction brakes. The above mentioned challenges will lead to a change of the friction couple properties. The reduced energy requirements and consequently reduced temperature level of the friction pair, in combination with very high and respectively very low rubbing speeds is a significant factor for the design and development of friction materials for hybrid brake systems. These altered load conditions result in new design and optimisation possibilities of the brake system and friction pair.
The influence of regenerative braking on the development of friction materials
Einfluss der Nutzbremsung auf die Entwicklung von Friktionswerkstoffen
2010
14 Seiten, 9 Bilder, 1 Tabelle, 4 Quellen
Conference paper
English
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