INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To improve efficiency of an internal combustion engine.SOLUTION: An internal combustion engine includes a compression ratio variable mechanism capable of changing a compression ratio. Exhaust gas outflowing from a combustion chamber contains unburned fuel and thereby unburned fuel loss occurs. The internal combustion engine estimates a change rate of the unburned fuel loss with respect to a compression ratio when the compression ratio changes, and a change rate of theoretic thermal efficiency with respect to the compression ratio when the compression ratio changes. Moreover, the internal combustion engine changes the compression ratio toward a compression ratio in which the change rate of the unburned fuel loss and the change rate of the theoretic thermal efficiency matches.