PURPOSE: To prevent a large amount of fuel gas from being supplied to a subcombustion chamber at the time of cutting off an engine load by providing a communication path, connecting a fuel gas passage to a charge air passage in the downstream, and also an electromagnetic opening/closing valve, opened only for a fixed time at the time of cutting off the engine load, in this communication path.
CONSTITUTION: When an opening of the second new charge air pipe 22 is minimized by actuating a throttle valve 40 by a load cut off signal, a new charge air amount, supplied to a main fuel chamber 6, is suddenly decreased. Simultaneously, also a fuel gas amount, passing through each regulator 41a, 41b, is decreased. However, fuel gas is left in a fuel gas passage in the downstream. Here, the fuel gas passage in each gas main pipe 32a, 32b in the downstream is connected to a new charge air passage between each air filter 16a, 16b and each mixer 15a, 15b respectively by each communication path 60a, 60b. Each electromagnetic opening/closing valve 61a, 61b of normally closed type is arranged respectively in each communication path 60a, 60b, and these valves are opened only for a fixed time by a control unit 115 based on the load cut off signal.
NISHIZAWA HIRONORI
KASAI MICHIO
