초록 ▼

A catalyst (9) is disposed in an exhaust passage (8) of an internal combustion engine (1) for trapping nitrogen oxides in the exhaust from a fuel mixture of a lean air-fuel ratio and reducing trapped nitrogen oxides in the exhaust from a fuel mixture of an air-fuel ratio other than the lean air-fuel

A catalyst (9) is disposed in an exhaust passage (8) of an internal combustion engine (1) for trapping nitrogen oxides in the exhaust from a fuel mixture of a lean air-fuel ratio and reducing trapped nitrogen oxides in the exhaust from a fuel mixture of an air-fuel ratio other than the lean air-fuel ratio. The catalyst (9) also traps sulfur oxides in the exhaust when the catalyst temperature is less than a predetermined temperature, and discharges the trapped sulfur oxides when the catalyst temperature rises above the predetermined temperature. A microprocessor (10) calculates for example the sulfur oxide stored amount of the catalyst (9) based on engine running conditions, and determines that sulfur oxide discharge condition is satisfied when the sulfur oxide stored amount exceeds a predetermined amount. When the discharge condition is satisfied, the microprocessor (10) controls the fuel injection amount and fuel injection timing of the fuel injector (6) so as to generate a stratified air-fuel mixture in the combustion chamber (3). The stratified air-fuel mixture comprises a first layer surrounding the spark plug (7) and a second layer situated outside the first layer. The first layer comprises an atomized air-fuel mixture of a rich air-fuel ratio within an ignitable range. The second layer is leaner than the first layer.

대표청구항 ▼

1. A catalyst temperature control device for use with an internal combustion engine, the engine comprising a combustion chamber, a fuel injector which injects fuel into the combustion chamber, a spark plug which ignites an air-fuel mixture inside the combustion chamber, an exhaust passage which disc

1. A catalyst temperature control device for use with an internal combustion engine, the engine comprising a combustion chamber, a fuel injector which injects fuel into the combustion chamber, a spark plug which ignites an air-fuel mixture inside the combustion chamber, an exhaust passage which discharges exhaust in the combustion chamber, and a catalyst provided in the exhaust passage for trapping nitrogen oxides in the exhaust from a fuel of mixture of a lean air-fuel ratio and reducing trapped nitrogen oxides in the exhaust from a fuel mixture of an air-fuel ratio other than the lean air-fuel ratio, the catalyst also trapping sulfur oxides in the exhaust when a catalyst temperature is less than a predetermined temperature, and discharging trapped sulfur oxides when the catalyst temperature is greater than the predetermined temperature, the device comprising:a sensor which detects an engine running state; a microprocessor programmed to: determine whether or not a condition for discharging the sulfur oxides trapped by the catalyst is satisfied based on the running state; and control a fuel injection amount and a fuel injection timing of the fuel injector, when the discharging condition is satisfied, so as to generate a stratified air-fuel mixture in the combustion chamber, the stratified air-fuel mixture comprising a first layer surrounding the spark plug, the first layer comprising an atomized air-fuel mixture of a rich air-fuel ratio within an ignitable range, and a second layer leaner than the first layer situated outside the first layer; and a sensor which detects the catalyst temperature; and wherein the microprocessor is further programmed to control the fuel injection amount of the fuel injector, when the stratified air-fuel mixture is generated, such that the mean air-fuel ratio of the combustion chamber is maintained at the stoichiometric air-fuel ratio when the catalyst temperature is lower than a predetermined second temperature (Tcat2), and control the fuel injection amount of the fuel injector, when the stratified air-fuel mixture is generated, such that the mean air fuel-ratio of the combustion chamber is maintained at a rich air-fuel ratio when the catalyst temperature exceeds the second temperature (Tcat2).