Hydraulic systems in passenger cars rely on positive displacement pumps that have a pulsating flow rate due to geometrical reasons. The resulting pressure pulsation, causes solid-borne sound and finally audible air borne sound. Especially the hydraulic cylinder of the hydraulic power steering (HPS) gear is a source of air borne sound. It is therefore the task to reduce the pressure pulsation before the flow reaches the steering gear. This is commonly done by a series of flexible hydraulic hoses. Due to their volumetric compliance, they work as low pass filters. During a pressure hill, they store hydraulic fluid and during a pressure valley, they release stored fluid. Damping of undesired pressure pulsation in the hydraulic system of passenger cars is currently done by passive elements such as throttle orifices; the higher the pressure loss due to the flow, the higher the attenuation of the pressure pulsation. However, damping is often not necessary below a certain system pressure and thus a gain in system efficiency can be achieved by by passing the resistive elements, depending on the load cycle. To create a compact solution, a system-pressure-actuated valve has been designed that can be integrated into an existing hydraulic hose and switches between a low resistance damping position and a high-resistance damping position depending on the system pressure. By experiments and simulations, it is shown that the valve can extend the catalogue of damping measures and, depending on the load cycle, has little impact on overall system efficiency. Simulative results have shown that the reduction of energy consumption does not exceed with the currently available switch-on/switch-off pressure levels. For load cycles with a high mean pressure, the adaptive system can even create a worse energy balance than the passive solution. Generally, the valve offers better results the lower the mean pressure and the higher the flow rate. Further improvements seem possible with higher thresholds for the valve actuation, but at the risk of higher noise emissions. In its current form, the valve can represent an addition to the existing damping devices, but it has to be used in conjunction with classic methods. To compare the energy efficiency of different design solutions the load cycle has to be taken into consideration.


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    Titel :

    Power demand of load adaptive attenuation of pressure pulsation in automotive systems


    Weitere Titelangaben:

    Energiebedarf der lastadaptiven Pulsationsminderung im Kraftfahrzeug


    Beteiligte:
    Rösner, J. (Autor:in) / Pelz, P. (Autor:in) / Bootz, A. (Autor:in) / Kemnitz, R. (Autor:in)


    Erscheinungsdatum :

    2008


    Format / Umfang :

    25 Seiten, 9 Bilder, 2 Tabellen, 5 Quellen


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Print


    Sprache :

    Englisch




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