The Potential of the Ceramic Valve in IC Engines 2003-32-0032
Recently, control of the gas-exchange process has come into focus as a critical element of the development process for internal combustion (IC) engines. The information learned in various engine development organizations worldwide has recently been put into practice via the introduction of many variable valve control strategies. The intention of these strategies ranges from simple enhancement of volumetric efficiency to completely controlling the combustion process at various engine speeds. The challenge to engine designers is mainly to reduce the relatively high masses of the valve actuating elements while increasing the stiffness to positively affect the dynamic behavior of the valve actuation system. Other benefits of a light-weight valve train is the reduction of the required energy to displace the valve element, which results in a more compact (lighter) cylinder head construction.
In the search for alternative valve materials, it was discovered that Silicon Nitride Ceramic (SiN or “ceramic”) was ideally suited for the poppet-valve component. A study was initiated in partnership with Ford Motor Company and Hoechst, to determine the viability of the application in a modern cylinder head concept. Simulations of the valve train were undertaken to determine dynamic behavior, resulting forces generated, frictional behavior, and component stress. Simultaneously, the testing department at Schrick prepared special test equipment and procedures to verify the calculated results. This work details some pertinent data that resulted from this exercise.
The focus of this development was not only to verify the material capability, but also to study its ability to enhance engine / cylinder head performance when the adjacent components were designed to take full advantage of the Silicon Nitride material properties.
The ability of the application to enhance engine friction characteristics, noise vibration and harshness (NVH), available engine torque, and emissions and fuel economy is the subject of this work. The material also showed improved wear characteristics over the duration of the testing.