Failure Modes and Reliability Analysis of Belt-Type CVT Systems for Scooters

The purpose of the present study is to carry out failure analysis of a scooter's continuously variable transmission (CVT) system that is considered to be one of the key components of the scooter. In the study, many reliability analytical tools such as failure mode, effect and criticality analysis (FMECA) and fault tree analysis (FTA) are used to identify possible failure modes of the CVT system and its subsystems. The failure effects of components on the CVT system are emphasized in particular. Aside from the qualitative evaluation, simulation algorithms are also developed to examine the performance of the CVT system and assess the reliability of the belt. Through the study, it is found that mechanical wear at both sides of the V-belt is the most serious problem that affects the CVT performance. The sliding collar of the driven pulley is another component that has to be observed carefully. Some design improvements are pointed out at the end of the paper.