Patent ID: 7252069

Claim:
A gas fuel engine operating with gas fuel, comprising: a combustion chamber formed by a cylinder and a piston; an injector for injecting fuel to form an air-fuel mixture in the combustion chamber; a spark plug provided at a cylinder head for igniting the air-fuel mixture; and a control unit for controlling an amount of fuel to be injected by the injector, wherein the fuel is injected by the injector twice for each combustion stroke, a first injection of the fuel is performed in a first combustion period to form a first air-fuel mixture having a local excess air factor not less than 2, a second injection of the fuel is performed in a second combustion period to form a second air-fuel mixture having a local excess air factor less than 1.1, the first injection is switched to the second injection during one cycle of the combustion stroke, and an interval of a crank angle, during which the fuel is not injected by the injector between the first and second injections, is controlled such that the interval becomes shorter as an engine rotational speed becomes higher.