US Patent 7802556 Homogeneous charge compressed ignition engine operating method

A method is provided for operating a homogeneous charge compressed ignition engine in which a mixture gas is burned by compression ignition in a combustion chamber of a cylinder, fuel and air being previously mixed to produce the mixture gas. The homogeneous charge compressed ignition engine includes an ignition plug, which performs spark ignition to the mixture gas. An advance-angle limit and a delay-angle limit of spark ignition timing are set. The compression ignition of the mixture gas is able to be induced at the spark ignition timing. The spark ignition is supplementarily performed to the mixture gas according to an operating condition between the advance-angle limit and the delay-angle limit.