Stuttgart – Daimler Buses is cutting buses' fuel consumption thanks to electrohydraulic power steering (EHPS). The fully integrated system replaces the conventional power steering pumps used nowadays in all buses with a gross weight of over 7.5 t. Thanks to the demand-based actuation of the electric power steering pump, which had previously been powered by the internal combustion engine, steering assist can in future be used regardless of the engine speed.
As it can be freely positioned in the vehicle, the unit, consisting of a three-phase current synchronous motor, control unit, high-performance electrical system and hydraulic pump in a single housing, enables simple visual inspections of the power steering fluid reservoir and its fill level. Short hydraulic pipes also ensure system-based friction loss is significantly reduced within the hydraulic circuit. The intelligent control system converts vehicle data to a demand-based actuation of the electrically operated 24 V pump – consequently, it provides the right amount of steering assistance depending on the driving situation. Summing up, the net result is a significant fuel saving.
The system, developed in collaboration with the Engineering Center Steyr GmbH & Co. KG, based in the Austrian town of St. Valentin, has been awarded the "Innovation Label" by the specialist panel of the European Coach Week (ECW) at the international Busworld 2015 specialist trade fair in Kortrijk, Belgium.It is planned to offer the system for Mercedes-Benz Citaro city buses as optional equipment from mid-2017.