Patent ID: 7004116

Claim:
A method of operating a four-stroke internal combustion engine having an exhaust stroke and an intake stroke, and including inlet valve means to regulate flow of air into a combustion chamber, exhaust valve means to regulate flow of combusted gases from the combustion chamber, and injection means to inject fuel directly into the combustion chamber, the method comprising the steps of: closing the exhaust valve means prior to the end of the exhaust stroke to trap combusted gases in the combustion chamber; injecting fuel directly into the combustion chamber into the combusted gases trapped in the combustion chamber after closing of the exhaust valve; opening the inlet valve means during the intake stroke following the step of injecting fuel directly into the combustion chamber into the combusted gases to admit charge air into the combustion chamber to be mixed with the previously trapped combusted gases; and injecting fuel directly into the combustion chamber into the mixture of the trapped combusted gases and the charge air introduced during the intake stroke under control of the inlet valve means; whereby: in the combustion chamber conditions are generated which enable the mixture of fuel, air and combusted gases to combust by auto-ignition with the combusted gases expanding during the power stroke; and wherein: said steps of injecting fuel comprise injecting said fuel with an air assist fuel injector which uses compressed air to entrain fuel to be delivered into the combustion chamber.