Germany-based Mobil Elektronik has developed a hydraulic power unit designed to provide rear axle steering in truck applications. The Hydraulic Power Pack was originally developed for the company’s EHLA (Elektronisch-Hydraulische Lenk-Anlage) electronic-hydraulic rear power steering systems used in vehicles and equipment.
The hydraulic pump is driven by a synchronous electric motor that consumes energy only if the rear axle is being steered and hydraulic oil is required. Thus, a hydraulic supply that is independent from the power takeoff of the vehicle’s diesel engine results in overall energy savings, the company said.
The EHLA system allows the steering angle of the rear axle to be set independent of the front axle. At low speeds the steering angle can be set to its maximum for a better maneuverability, while a steering angle decrease dependent on speed to increase driving stability is also possible.
At higher speeds, such as in long highway drives, the axle is typically set to the middle position and does not steer beyond a defined threshold. According to Mobil Elektronik, a fuel consumption decrease of around 0.2 gal. per 100 miles is realistic in comparison to permanently running PTOs.
The Hydraulic Power Pack can be used if no mechanical power take-off (PTO) is available for an additional hydraulic pump. This means that the auxiliary steering system with Hydraulic Power Pack can be adapted to nearly any vehicle independent from the manufacturer, Mobil Elektronik said.
Installation of the system is designed to be simple. After installation on the vehicle frame, cables to the steering cylinder, the tank and a signal cable to the steering computer are added. Because of the integrated hydraulic unit, the Hydraulic Power Pack can directly be connected to the steering cylinder. Mobil Elektronik also offers a completely wired stainless steel box which contains a safety steering computer, the hydraulic tank and the Hydraulic Power Pack.
The Hydraulic Power Pack utilizes a 2.3 kW synchronous electric motor with integrated power electronics and a pump. The pump provides a flow rate of up to 3.43 gpm at pressures up to 2300 psi. This enables to the system to steer a 13.2 ton axle with maximum load from a standstill, the company said.
The safety steering computer that communicates via CAN bus with the Hydraulic Power Pack monitors and controls the direction of rotation of the engine, the engine speed as well as the engine status of the Hydraulic Power Pack, along with the movement of the auxiliary steering axle. Adjustments to the vehicle’s geometry and different customer requirements on steering performance can be done acting on the system’s parameters, Mobil Elektronik said.