Durability and Reliability Demonstration for Switching Roller Finger Follower in Cylinder Deactivation Systems

Cylinder deactivation (CDA) is an effective method to adjust the engine displacement for maximum output and improve fuel economy by adjusting the number of active cylinders in combustion engines. A Switching Roller Finger Follower (SRFF) is an economic solution for CDA that minimizes changes and preserves the overall width, height, or length of Dual Overhead Cam (DOHC) engines. The CDA SRFF provides the flexibility of either transferring or suppressing the camshaft movement to the valves influencing the engine performance and fuel economy by reducing the pumping losses. This paper addresses the performance and durability of the CDA SRFF system to meet the reliability for gasoline passenger car engines. Extensive tests were conducted to demonstrate the dynamic stability at high engine speeds and the system capacity of switching between high and low engine displacement within one camshaft revolution. The system durability was demonstrated with high and low engine speeds, various oil temperatures, mode switching, and abuse tests, meeting the end of life criteria in wear and function. System robustness to dimensional variation was tested to understand the effect on performance and durability. Lash increase, one important metric for wear evaluation, was monitored during durability and abuse tests. Multiple life tests were performed to demonstrate the system reliability of 99.94% over the engine's useful life. Test results show a robust design for performance, durability, and reliability for passenger car applications.