F2010A032
APPLICATION OF FUEL AND COST EFFICIENT STEERING TECHNOLOGY - VARIABLE DISPLACEMENT PUMP - TO SUV/SUTS
With the increasing severity of global financial and fuel economical crises, developing technologies which can address environmental pressures as well as provide cost efficiency is now more urgent than ever during vehicle development. Steering variable displacement pump (VDP) technology is a fuel efficient yet cost efficient steering technology which has been applied to small vehicles. For heavier vehicles, such as SUV / SUTs, it is important and necessary to enable the potential application of VDP technology before electric power steering technology become ready in terms of system capacity and cost.
However, it is challenging to apply VDP technology to heavier vehicles due to technical difficulties to achieve good marketability performance. Larger displacement and higher pressure of power steering pump are required for heavier vehicles due to increased steering rack load, comparing to smaller vehicles. Larger displacement and higher pressure potentially cause higher level of steering noise. Furthermore, due to the unbalanced mechanism of its unique design, VDP inherently produces higher level of noise than conventionally-used constant displacement pump.
During this study, thorough investigation is conducted on a SUV with the integration of a VDP, in three critical aspects including noise characteristics, fuel economic benefit and steering performance. Firstly, a method based on the theory of fluid pressure wave propagation for evaluating the source noise characteristics of the VDP is developed, and a strong correlation between the measured characteristics of the pump unit and the subjective feeling judgment of vehicle noise performance is established. Then, by utilizing the method and the correlation as valuable tools, problem areas of noise performance are identified. Based on the analysis of the source noise characteristics, design improvement measures for improving both the source noise of the VDP as well as the noise attenuation characteristics of the steering system are proposed and implemented. As the result, significant reduction in noise level at pump's dominant harmonics is achieved. Also presented in the paper are the experimental confirmation of fuel economic benefits and steering performance of the vehicle. Satisfactory results are achieved in both noise performance and fuel consumption reduction while without compromising vehicle steering performance.
This abstract is supplemented by a PDF, which can be viewed here.