Sensing and acting elements to guarantee the locking functions of seat belt retractors can emit noise when the retractor is subjected to externally applied vibrations. For these elements to function correctly, stiffness, inertia and friction needs to be in tune, leading to a complex motion resistance behavior, which makes it delicate to test for vibration induced noise. Requirements for a noise test are simplicity, robustness, repeatability, and independence of laboratory and test equipment.
This paper reports on joint development activities for an alternative test procedure, involving three test laboratories with different equipment. In vehicle observation on parcel shelf mounted retractors, commercially available test equipment, and recent results from multi-axial component tests [1], set the frame for this work. Robustness and reliability of test results is being analyzed by means of sensitivity studies on several test parameters. This work aims to obtain fundamental findings for retractor noise testing, which should be addressed by any general test procedure, to provide a maximum of repeatability and reliability.
Combining the knowledge about field relevant retractor noise sources from bench testing with CAE based [2] predictions of the retractors’ in-vehicle behavior can yield much easier and quicker in a suitable acoustic in-vehicle performance.