| 摘要 |
PROBLEM TO BE SOLVED: To maintain an active state of a catalyst in an engine constituted to reduce an exhaust loss.SOLUTION: A controller 100 performs lean combustion by injecting fuel via a fuel injecting valve 33 so that G/F is equal to or more than 30 in a low load region. When under an operating condition within a low load region, if an active state of a catalyst is found to be lower than a prescribed value, fuel is injected within a period from a later phase of the compression stroke to an early phase of the expansion stroke so as to interpose a gas layer not contributing to combustion around an outer peripheral surface of a combustion chamber 17, and an amount of fresh air to be guided to a cylinder (cylinder 11) is decreased below that in the case that the active state of the catalyst is at a predetermined level or more, thereby producing and burning an air-fuel mixture with an air-fuel ratio A/F of 12.5 to 15.0 in a central portion enclosed by an outer periphery of the combustion chamber. |
