Failure assessment using accelerated testing on IC engine’s starter motor for reliability improvement

Abstract

Generally, starter motors are tested at increased usage rate to verify the durability of the component and to identify the premature failure aspects in the controlled ambient environment. During the process, the latent failures which exhibit unique failure modes at variable environment are hidden, which can impact the warranty of the product. Specifically the Stop–Start (SS)-type starter motors, which often work under increased thermal condition, may show latent failures. Principally, a starter motor is mounted over the IC engine where the working temperature is always between 60 and 120 °C, to establish easy contact with the engine flywheel during cranking. Hence, identifying the latent failures of the starter motor at increased thermal condition is useful to ensure the reliability of the motor as per the requirements of automotive manufacturers. This paper emphasis to improve the reliability of the starter motor’s commutator for high-temperature applications, which may exhibit the failure mode of “Commutator Segment Lift”. The said analysis is performed using time-to-failure data from the laboratory testing of proto samples. This reliability study for the design improvement on commutator includes failure mechanism study, failure source identification and failure improvement.