Power plants – Internal combustion engine with treatment or handling of... – Methods
Patent
1996-11-19
1998-07-07
Hart, Douglas
Power plants
Internal combustion engine with treatment or handling of...
Methods
60286, 60301, 023430, F01N 320
Patent
active
057750998
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of purifying the exhaust of an internal combustion engine.
BACKGROUND ART
An internal combustion engine which provides in the engine exhaust passage an NO.sub.x absorbent which absorbs NO.sub.x when the air-fuel ratio of the inflowing exhaust gas inflowing into the NO.sub.x absorbent is lean and releases the absorbed NO.sub.x when the air-fuel ratio of the inflowing exhaust gas is made the stoichiometric air-fuel ratio or rich and is designed to normally make the air-fuel ratio of the air-fuel mixture supplied to the engine lean and at this time make the NO.sub.x exhausted from the engine be absorbed by the NO.sub.x absorbent and to make the air-fuel mixture supplied to the engine rich when causing the releasing of the NO.sub.x absorbed in the NO.sub.x absorbent has already been proposed by the applicant (see PCT International Publication WO93/07363).
However, in a stratified combustion type internal combustion engine designed to stratify the air-fuel mixture formed in the combustion chamber so as to form an air-fuel mixture ignitable in a limited region of part of the inside of the combustion chamber, when this type of stratification action is performed, if the supplied fuel were merely increased so as to change the average air-fuel ratio inside the combustion chamber from lean to rich so as to releasing the NO.sub.x from the NO.sub.x absorbent, the air-fuel mixture formed in the limited region of part of the inside of the combustion chamber would become overly rich and as a result the spark plug would not be able to ignite the air-fuel mixture well, so there would be the problem that misfires would occur.
Further, if, as in the above internal combustion engine, the air-fuel mixture supplied to the engine were merely made rich so as to releasing the NO.sub.x from the NO.sub.x absorbent, the output torque of the engine would rapidly increase, so the problem would also arise that a shock would be generated.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a method of purifying the exhaust able to prevent the occurrence of misfires when increasing the supplied fuel so as to releasing the NO.sub.x from the NO.sub.x absorbent.
According to the present invention, there is provided a method of purifying the exhaust of an internal combustion engine providing in the engine exhaust passage an NO.sub.x absorbent which absorbs the NO.sub.x when the air-fuel ratio of the inflowing exhaust gas inflowing into the No.sub.x absorbent is lean and releasing the NO.sub.x absorbed when the air-fuel ratio of the inflowing exhaust gas is made the stoichiometric air-fuel ratio or rich, wherein, when in a lean air-fuel mixture combustion operating state where the air-fuel mixture is burned in a state with a lean average air-fuel ratio in the combustion chamber, the air-fuel mixture formed in the combustion chamber is stratified to form an ignitable air-fuel mixture in a limited region of part of the inside of the combustion chamber and the NO.sub.x produced at this time is made to be absorbed in the NO.sub.x absorbent and when releasing the NO.sub.x from the NO.sub.x absorbent when in the lean air-fuel mixture combustion operating state, the average air-fuel ratio in the combustion chamber is changed from lean to the stoichiometric air-fuel ratio or rich and the amount of fluctuation of the ignitable air-fuel ratio of the air-fuel mixture formed in the limited region of part of the inside of the combustion chamber at this time is made smaller than the amount of reduction of the average air-fuel ratio.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overview of an internal combustion engine showing by a cross-section the engine body,
FIG. 2 is a plan view schematically showing the overall internal combustion engine shown in FIG. 1,
FIG. 3 is a plan cross-sectional view of a cylinder head,
FIG. 4 is a plan view of a piston top surface,
FIG. 5 is a side cross-sectional view of FIG. 3,
FIG. 6 is a view showing the fuel injection amount and
REFERENCES:
Bulletin of The Japan Institute of Metals (1993), vol. 32, No. 5, pp. 441-443.
Ito Yasushi
Mashiki Zenichiro
Hart Douglas
Toyota Jidosha & Kabushiki Kaisha
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