Identify and improve the failure mechanism of contact failure in multifunction switches by developing sequential test methods

Abstract

Contact failure and light malfunction are common problems in multifunction swit- ches. Fretting refers to surface degradation in mechanical components. Two materials pressed together by an external static load are subjected to a transverse cyclic load or various vibrations, causing wear. Numerous studies have been conducted to address the problem of chronic signal loss. However, the cause of failure in the early stages remains obscured. The field failure analysis shows that the contact pressure decreases even at low mileage (<10000 km). Meanwhile, the finite element method analysis demonstrates that the contact pressure decreases during the assembly process of multifunction switches. We validated that high-temperature-induced creep and vibration are the primary causes of failure in multifunction switches through a series of tests. Although conventional testing methods consist of unit evaluations to verify specific failure mech- anisms, such as high-temperature exposure and vibration, and cannot reproduce actual failures, the series test method can reflect actual failure phenomena. Additionally, benchmarking with competitors confirmed that the round design structure mitigates the reduction in contact pres- sure. Furthermore, we provided guidelines for improvement from quality and design perspec- tives. The most important result of this study was the identification of the failure mechanism of multifunction switches through the series test method, and creep (high temperature) has a stronger effect on the degradation of contact dimensions and pressure than vibration.