Mobile Fluid Power Systems Design: with Focus on Energy Efficiency

This work deals with innovative energy efficient fluid power systems for mobile applications. The subjects taken up concern to what extent and how energy losses can be reduced in mobile working hydraulics systems. Various measures are available for increasing energy efficiency in these kinds of systems. Examples include: Flow controlled systems The pump controller is switched from a load sensing to a displacement controlled one. The displacement is controlled in an open loop fashion directly from the operator’s demand signals. This reduces energy consumption at the same time as dynamic issues that are attached to LS systems can be avoided. Individual metering valve systems Flexibility is increased by removing the mechanical coupling between the meter-in and meter-out orifices in directional valves. An overview of this kind of system is given in the thesis. A design proposal that has been implemented is also presented. Initial test results are shown. Patents for this particular system have been applied for. Displacement control Metering losses are reduced by removing the directional valves. One pump is used for each load in such systems. This hardware layout involves considerable changes compared to conventional systems. Displacement controlled systems are not studied in this work. In mobile applications, overall efficiency is often poor and losses are substantial. The measures listed above can help improve this significantly in such applications. A flow dividing system can decrease energy consumption by about 10% and an individual metering system by about 20%. Losses in pump controlled systems are difficult to give a figure for; the losses are rather attached to the pumps and motors and not to the system layout. However, the losses for these systems are presumably even lower than for individual metering systems. The main focus in this work is on individual metering systems but questions about which components and so on are also treated. For example, the Valvistor valve concept has been studied as part of this work.