초록 ▼

There are provided NOx trap catalyst to trap and release NOx based on air-fuel ratio, first fuel supply means for supplying gasoline, second fuel supply means for supplying hydrogen, engine operation detecting means for detecting engine operating condition, fuel ratio changing means for changing the

There are provided NOx trap catalyst to trap and release NOx based on air-fuel ratio, first fuel supply means for supplying gasoline, second fuel supply means for supplying hydrogen, engine operation detecting means for detecting engine operating condition, fuel ratio changing means for changing the ratio of gasoline and hydrogen, NOx release determining means for determining whether it is required for the NOx to be released based on a state of the trapped NOx, NOx releasing means for releasing the NOx trapped by making the air-fuel ratio rich when the NOx releasing requirement is determined, gasoline ratio increasing means for increasing the ratio of gasoline when NOx releasing requirement is determined and the air-fuel-ratio rich control is executed. Accordingly, improper vibrations or noises can be restrained from occurring when the rich air-fuel-ratio control is executed to release the trapped NOx from the NOx trap catalyst.

대표청구항 ▼

What is claimed is: 1. 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

What is claimed is: 1. 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. 2. The control device of a hydrogen engine of claim 1, wherein said fuel ratio changing means is configured so as to switch the fuel supplied between the fossil fuel only and the hydrogen fuel only based on the engine operating condition, and said fossil-fuel ratio increasing means is configured so as to switch the fuel supply from the hydrogen fuel only to the fossil fuel only 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, in a current engine operating state where only the hydrogen fuel is supplied into the combustion chamber. 3. The control device of a hydrogen engine of claim 1, wherein said fuel ratio changing means is configured so as to switch the fuel supplied between the fossil fuel only and both the fossil fuel and the hydrogen fuel based on the engine operating condition, and said fossil-fuel ratio increasing means is configured so as to increase 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, in a current engine operating state where both the fossil fuel and the hydrogen fuel are supplied into the combustion chamber. 4. The control device of a hydrogen engine of claim 1, wherein said fuel ratio changing means is configured so as to change the fuel supplied among the fossil fuel only, the hydrogen fuel only and both the fossil fuel and the hydrogen fuel based on the engine operating condition, and said fossil-fuel ratio increasing means is configured so as to increase the ratio of the fossil fuel supplied into the combustion chamber relative to the hydrogen fuel supplied or change to the fossil fuel only 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, in a current engine operating state where both the fossil fuel and the hydrogen fuel are supplied into the combustion chamber, whereas said fossil-fuel ratio increasing means is configured so as to change the fuel supply to the fossil fuel only or both the fossil fuel and the hydrogen fuel 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, in a current engine operating state where only the hydrogen fuel is supplied into the combustion chamber. 5. The control device of a hydrogen engine of any one of claims 1 through 4, further comprising an acceleration detecting means for detecting an engine acceleration, wherein the air-fuel ratio of the fuel supplied into the combustion chamber is made rich when the engine acceleration is detected by said acceleration detecting means, without changing the fuel ratio set by said fuel ratio changing means. 6. The control device of a hydrogen engine of any one of claims 1 through 4, further comprising a sulfur-poisoning detecting means for detecting a parameter relating to a degree of sulfur-poisoning of said NOx trap catalyst, and a sulfur releasing means for releasing sulfur attached to said NOx trap catalyst by making the air-fuel ratio of the exhaust gas in a rich state when the degree of sulfur-poisoning detected by said sulfur-poisoning detecting means is greater than a specified value, wherein said fuel ratio changing means is configured so as to change the fuel ratio in such a manner that the ratio of the hydrogen fuel supplied into the combustion chamber relative to the gasoline fuel supplied during a first specified time period from a start of said air-fuel-ratio rich control by said sulfur releasing means is greater than that during a second time period after said first specified time period has passed. 7. The control device of a hydrogen engine of claim 6, further comprising an exhaust-gas temperature detecting means for detecting a parameter relating to a temperature of the exhaust gas, wherein said fuel ratio changing means is configured such that said first specified time period for a low exhaust-gas-temperature state is set to be longer than that for a high exhaust-gas-temperature state. 8. The control device of a hydrogen engine of claim 6, further comprising an exhaust-gas temperature detecting means for detecting a parameter relating to a temperature of the exhaust gas, wherein said increasing of the hydrogen-fuel ratio supplied into the combustion chamber by said fuel ratio changing means is configured so as to be restrained further in a high exhaust-gas-temperature state, compared with in a low exhaust-gas-temperature state. 9. 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 injector operative to supply a fossil fuel into a combustion chamber; a second fuel injector operative to supply a hydrogen fuel into the combustion chamber; a sensor operative to detect an engine operating condition; a control unit operative to receive a detective signal of said sensor and control said first and second fuel injectors, wherein said control unit is configured so as to change a ratio of the fossil fuel supplied into the combustion chamber relative to the hydrogen fuel supplied based on the engine operating condition, determine 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, release 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, and increase the ratio of the fossil fuel supplied into the combustion chamber relative to the hydrogen fuel supplied when the NOx releasing requirement is determined and the air-fuel-ratio rich control is executed.