Acoustic diagnosis of driving belt physical condition in enclosures

Timing belt transmission is a key subsystem of international combustion engines. Faults in such belt systems lead to power loss, increased emissions and, in case of failure, may even cause severe damage to the whole engine. Hitherto, the physical condition of the belt has been assessed manually, which is both inconvenient and inaccurate. It is well known that driving belts emit noise according to parametrical conditions such as speed of rotation, tension, structural integrity, etc. The analysis of belt behaviour and subsequent diagnosis of potential failure should preferably be carried out using non contact methods and, as such, acoustic diagnostic stands out as a promising method. One added problem in the diagnosis process is the noise generated by the engine and the acoustic behaviour of the enclosure where the measurement is taking place. This study investigates new approaches to measuring and analysing the acoustic emission from a belt at different conditions inside an enclosure. Techniques employing a combination of microphones in directional near-field and omni-directional elsewhere are used in order to obtain a better signal. Transfer function measurement techniques are applied in order to separate belt noise from engine noise and the acoustic response of the enclosure. The method allows the extraction of useful diagnostic information about the condition of the belt and indicates areas for further research.