Zeitschrift für angewandten Maschinenbau

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Investigation of Fluidborne Noise Reduction in Automotive Hydraulic PowerSteering Systems

Chuan-Chiang Chen, Olakunle Harrison and Adrian K. McKinney

The performance of a pulse suppressor, currently used to alleviate pump-induced noise in automotive power steering systems, was characterized in this research. A hydraulic test system was developed to evaluate the noise attenuation effects of a pulse suppressor as well as other devices. Four pressure transducers were used to measure the dynamic pressures in the pressure line at different locations (two before and two after the suppression device); thus it was possible to determine the transfer matrix elements relating line pressures to noise. The transmission loss (the criteria used to determine the noise isolation performance of a noise reduction device) for this device was also estimated. The test system was verified by using a 0.52-meter section of steel tubing. Good agreement was obtained between the experimental and theoretical matrix elements. The results show that the direction of a pulse suppressor plays a role in the attenuation of the pressure wave. Therefore, the symmetry of the suppressor cannot be assumed. Compared to other noise reduction devices (reinforced rubber hose, coaxial tuning cable and hose) the pulse suppressor provides good transmission loss. However, the overall system response is a function of frequency. It is suggested that various noise reduction devices be combined to achieve the greatest noise reduction. The methodology can be used to optimally reduce the pump-induced noise and vibration in hydraulic power steering systems during the design stage. With the experimentally determined transfer matrix for each device, the relationship between two ports can readily be obtained by matrix multiplication. The analysis presented in this investigation can be also applied to other fluid power systems (i.e., engine cooling systems and HVAC systems).