To prevent the temporary overlean state of an air fuel ratio after the release of an exhaust brake and to solve the deterioration of the drivability of a vehicle, the engine stall or the like in an exhaust brake device where a shutter valve of an exhaust path is closed during the operation of the exhaust brake of a LPG engine, so that the supply of the fuel to an inlet path is stopped and only the intake air is supplied to the engine, and the engine is operated as a compressor to obtain the braking force.
The fuel gas is forcibly supplied to an intake path of an engine from a secondary fuel supply device of a system different from that of an ordinary main fuel supply device during the passage of the predetermined times t1, t2 from a time when the operation of an exhaust brake is released, whereby the overlean of an air/fuel ratio caused by the delay of the supply of the fuel from the main fuel supply device in an initial period of the operation releasing state of the exhaust brake, can be prevented.
OKADA NOBUYOSHI
MORIHARA KATSUHIKO
MOTOSE YASUNORI
