Gas engine with pre-combustion chamber

Claim 1

A gas engine with pre-combustion chambers comprising: a cylinder head mounted on a cylinder block; valves for opening and closing ports formed in the cylinder head; combustion chamber structures installed in cavities in the cylinder head and having cylinders forming main combustion chambers; pre-combustion chamber structures arranged at substantially central parts of the combustion chamber structures and forming pre-combustion chambers; communication ports communicating the pre-combustion chambers to the main combustion chambers; control valves for opening and closing the communication ports; and fuel supply means for supplying gas fuel into the pre-combustion chambers; wherein the communication ports comprise main communication ports and sub-communication ports; wherein when the control valves are fully open the main communication ports and the sub-communication ports are open, and when the control valves are partly open the sub-communication ports are open, and wherein the control valves keep the communication ports closed during a length of time from a beginning of an intake stroke to near a top dead center of a compression stroke, the fuel supply means are open when the control valves keep the communication ports closed to thereby admit gas fuel into the pre-combustion chambers, the fuel supply means are then closed at near an end of a compression stroke while the control valves move towards the main combustion chambers to open the sub-communication ports whereby compressed air is permitted to flow from the main combustion chamber into the pre-combustion chamber through passages defined by a peripheral surface of bevel portions of the control valves and wall surfaces of the sub-communication ports, the compressed air being in the form of jet streams that are guided substantially tangentially along the peripheral surface of the bevel portions so as to avoid transverse collision against the bevel portions, and then, following compression-ignition and burning of a mixture of the compressed air and the gas fuel, full movement of the control valves opens the main communication ports so as to permit combustion gas from the pre-combustion chamber into the main combustion chamber at first through the sub-communication ports and sequentially through the main communication ports.