Patent ID: 7111452

Claim:
A control device of a hydrogen engine, comprising: a NOx trap catalyst disposed in an exhaust gas passage, the NOx trap catalyst trapping NOx in an exhaust gas when the exhaust gas is in a lean air-fuel-ratio state and releasing a trapped NOx when the exhaust gas is in a rich air-fuel-ratio state including a substantially stoichiometric air-fuel ratio; a first fuel supply means for supplying a fossil fuel into a combustion chamber; a second fuel supply means for supplying a hydrogen fuel into the combustion chamber; an engine operation detecting means for detecting an engine operating condition; a fuel ratio changing means for changing a ratio of the fossil fuel supplied into the combustion chamber relative to the hydrogen fuel supplied based on the engine operating condition detected by said engine operation detecting means; a NOx release determining means for determining whether it is required for the NOx trapped at said NOx trap catalyst to be released based on a state of the trapped NOx at said NOx trap catalyst; a NOx releasing means for releasing the NOx trapped at said NOx trap catalyst by making the air-fuel ratio of the exhaust gas in said rich state when the NOx releasing requirement is determined by said NOx release determining means; a fossil-fuel ratio increasing means for increasing the ratio of the fossil fuel supplied into the combustion chamber relative to the hydrogen fuel supplied when said NOx releasing requirement is determined by said NOx release determining means and said air-fuel-ratio rich control by said NOx releasing means is executed.