Patent ID: 7370616

Claim:
Method for control of transition between combustion modes of a direct-injection engine operable in a homogeneous charge compression ignition (HCCI) mode at lower loads and a spark ignition flame propagation (SI) mode at higher loads wherein the engine includes a variable valve actuation system including two-step high and low lift valve actuation and separate cam phasing for both intake and exhaust valves, the method comprising: operating the engine at steady state, with fuel-air-exhaust gas mixtures at predetermined conditions, for each speed and load, of fueling mass flow rate (fueling rate), injection timing (FI), spark timing (SI), throttle position, exhaust gas recirculation (EGR) valve setting, and exhaust recompression obtained by negative valve overlap (NVO) between closing of the exhaust valves and opening of the intake valves in each cylinder; controlling the engine during the HCCI mode by retarding exhaust valve opening and advancing intake valve opening to effect decreasing negative valve overlap with increasing engine load; and controlling the engine during mode changes between the HCCI mode and an SI mode by switching the exhaust and intake valves between low lift for HCCI operation and high lift for SI operation.