Daimler Buses Using Electrohydraulic Power Steering to Reduce Fuel Consumption

Daimler Buses has jointly developed an electrohydraulic power steering system which utilizes demand-based actuation of the electric power steering pump to provide fuel efficiency benefits.

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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 combustion engine, steering assist can in future be used regardless of the engine speed.

As a result of the conveniently positioned component 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 make sure 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 24V pump – consequently, it provides the right amount of steering assistance depending on the driving situation. All in all, this adds up to a significant fuel saving.

The system was developed in collaboration with the Engineering Center Steyr GmbH & Co. KG, based in the Austrian town of St. Valentin, and has already 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. The plan is to offer the system for Mercedes-Benz Citaro city buses as optional equipment from mid-2017.