Mobil Elektronik (Germany) shows at IAA 2018 its power hydraulic pack. It is suitable for rear-axle control.
One main argument for using a hydraulic supply that is independent from the power takeoff of the diesel engine is energy conservation. This is obvious since a synchronous electric engine drives the hydraulic pump. The electric engine only consumes energy, if the rear axle is actually steered and hydraulic oil is required. The steering angle of the rear axle can be set independent of the front axle. A steering angle decrease dependent on speed is also possible. At low speeds a maximum steering angle is possible to be very maneuverable. The higher the speed the more limited the steering angle is set, to increase driving stability. The axle will be set to the middle position and does not steer then anymore from a defined threshold on. The pump can be switched off completely. This is the case at long highway drives for instance. Around half a liter less fuel per 100 km is quite realistic that way in comparison to permanently running power takeoffs.
The mentioned speed thresholds for the steering angle decrease and other properties can be adjusted via parameters at EHLA steering system. According to the supplier, numerous of these hydraulic power packs have been used already in EHLA steering systems. The easy installation and adaption to different vehicles is much more important to the customers than the fuel economy, explained the supplier. Using the hydraulic power packs is of particular interest, if no mechanical power takeoff (PTO) is available for an additional hydraulic pump. Thus the auxiliary steering system with Hydraulic Power Pack can be adapted to almost every vehicle independent from the manufacturer. This makes it interesting for small vehicle manufacturers and retrofitters.
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