Control of autoignition timing in a HCCI engine

A method for controlling a four stroke internal combustion engine operating in a homogenous charge compression autoignition mode and having an intake valve at an intake port, an exhaust valve at an exhaust port, and combustion chamber, comprising:

• adjusting said exhaust valve relative to said intake valve to vary exhaust valve closing time before top dead center, independent of intake valve opening time after top dead center, over successive engine cycles to change autoignition timing in response to a change in operator demanded engine torque.

A system for controlling a four cycle internal combustion engine operating in a homogenous charge compression autoignition mode and having an intake valve, an exhaust valve and combustion chamber, comprising:

• a first variable valve timing mechanism for controlling opening time and closing time of said exhaust valve, said mechanism providing a closing time of said exhaust valve before top dead center, and
• a second variable valve timing mechanism for controlling opening time and closing time of said intake valve, independent of exhaust valve closing time before top dead center, to vary intake valve opening time relative to top dead center over successive engine cycles to control autoignition timing in response to a change in operator demanded engine torque.

A system for controlling a four cycle internal combustion engine operating in a homogenous charge compression autoignition mode and having an intake valve, an exhaust valve and combustion chamber, comprising:

• a first variable valve timing mechanism for controlling opening and closing time before top dead center, independent of intake valve opening time after top dead center, over successive engine cycles to control autoignition timing in response to a change in operator demanded engine torque, and
• a second variable valve timing mechanism for controlling opening and closing time of said intake valve after top dead center.

A method for controlling a four stroke internal combustion engine operating in a homogenous charge compression autoignition mode and having an intake valve at an intake port, an exhaust valve at an exhaust port, and combustion chamber, comprising:

• adjusting opening time of said intake valve relatie to top dead center and to said exhaust valve after said exhaust valve is closed before top dead center in an exhaust stroke, said adjusting occurring in an initial intake event occurring before top dead center and in a subsequent intake event occurring after top dead in a manner to vary amount of residual burned gas in the combustion chamber flowing to the intake port in the exhaust stroke and back to the combustion chamber in an intake stroke to change autoignition timing in response to a change in operator demanded engine torque.

A method for controlling a four stroke internal combustion engine operating in a homogenous charge compression autoignition mode and having an intake valve at an intake port, an exhaust valve at an exhaust port, and combustion chamber, comprising:

• adjusting said exhaust valve relative to said intake valve before said intake valve is opened after top dead center during an intake stroke so as to vary exhaust valve closing time relative to top dead center in a manner to vary amount of residual burned gas in the combustion chamber flowing to the exhaust port in an exhaust stroke and back to the combustion chamber in the intake stroke to change autoignition timing in response to a change in operator demanded engine torque.