Daimler Buses has developed new electrohydraulic power steering systems (EHPS) together with the Austrian supplier Engineering Center Steyr GmbH & Co. KG. Conventional power-steering pumps in today's buses with a GVW of over 7.5 tonnes can be replaced by these.
Previously the power-steering pump was driven by the combustion engine. With the new system it can be actuated on demand. The power assistance for the steering is thus independent of the engine rpm.
Power assistance for the steering on demand
The new component consists of a three-phase synchronous motor, control unit, high-performance electronics and hydraulic pump in one casing. It is freely located in the vehicle. A simple visual check of the steering oil reservoir and of the level is therefore possible. Shorter hydraulic lines also result in considerably fewer systemic friction losses in the hydraulic circuit. The intelligent control system converts the vehicle data into demand-oriented control of the 24 V pump, which is electrically operated. Therefore, from driving situation to driving situation exactly as much steering assistance as necessary is provided; the fuel consumption falls considerably.
From mid-2017 onwards the system will be available for the Mercedes-Benz urban buses of the Citaro model as optional equipment. Back in 2015 at the international specialist fair Busworld 2015 in Kortrijk, Belgium, it received the “Innovation Label” from the expert jury in European Coach Week (ECW).