A study was undertaken to investigate the dependence of valve train sound quality on certain camshaft machining parameters. In particular, a sound quality issue referred to as camshaft chatter was investigated. Camshaft chatter refers to a noise caused by geometrical undulations on the camshaft lobes that excite valve train and cylinder head vibration modes during operation. The undulations are an artifact of the manufacturing process.; The engine used in the study was a dual overhead camshaft (DOHC) V6. Eight different left-hand-side exhaust camshafts were manufactured with different, known combinations of the selected machining parameters. Each parameter was varied between a “high” and “low” setting.; Tri-axial accelerometers were mounted at two locations on the cylinder head of the test engine, and extensive vibration data was collected for each camshaft.; The vibration data was analyzed using a number of methods, including: time domain analysis, RMS analysis, angle domain variance analysis, and RPM-frequency analysis.; After a method was developed to objectively quantify the severity of camshaft chatter, a main effects analysis was performed to assess the impact of the individual machining inputs.; It was found that vibration of the camshaft grinding wheel had the largest impact on camshaft chatter, followed by vibration of the grinding wheel motor. Tension of the drive belt was also shown to impact the severity of the chatter phenomenon.
展开▼
