Patent ID: 8826883

Claim:
A spark ignition gas engine comprising: a spark plug fitted on a fitting seat surface; a mounting hardware piece having the fitting seat surface therein; a fuel passage provided in the mounting hardware piece; a pre-combustion chamber disposed under the spark plug; a cylinder head for housing the spark plug, the mounting hardware piece being provided in the cylinder head; a fuel inlet connecting piece connected to the mounting hardware piece to supply fuel gas from the fuel inlet connecting piece to the pre-combustion chamber through the fuel passage, the fuel gas supplied in the pre-combustion chamber being ignited by spark discharge at the spark plug; a fuel inlet passage bored in the fuel inlet connecting piece; a solenoid valve that is provided at an inlet end of the fuel inlet connecting piece and is configured to perform open-close control of the fuel gas which streams into the fuel inlet passage; and a first check valve that is provided in the fuel inlet passage at a location nearer to the solenoid valve than the pre-combustion chamber relative to the spark plug so that combustion gas generated in the pre-combustion chamber is prevented from flowing backwards in a direction from the pre-combustion chamber toward the solenoid valve.