Detecting nicked automotive transmission gears in the final inspection by multi-scale time synchronous averaging

The present paper describes an inspection method for gear nicks at the final assembly process for automotive transmissions. This method applies multi-scale time synchronous averaging and optimal filtering to ensure the quality of transmission gears against abnormal noise due to gear nicks. At present, a highly reliable method has been developed for measuring gear noise in the final transmission assembly inspection process. However, the inspection system has realized not to evaluate nick-induced noise quantitatively. Therefore, the nick noise evaluation still relies on skilled workers who can estimate it subjectively. Eventually, it may reveal nick-induced noise on rare occasions after mounting the transmission on a vehicle. To avoid that requires the mechanism of nicks-induced vibration to be apparent. This paper proposes a method that can detect nick-induced vibration with high reliability. It also enables itself to identify a nicked gear even among several gears on a shaft in a transmission. The proposed method was implemented in the test equipment for the final assembly inspection and used to measure the noise of CVT units built with nicked gears. The results confirmed that this method allows itself to detect nicks that were hard to discern in subjective estimations and leads to making it possible to identify nicked gears. This method secures quality assurance against abnormal noise induced by transmission gear nicks.